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Home » Auto Ownership

The Service Engine Light: Your Mechanics Dirty Little Secret

Last updated by on August 6, 2016

Troubleshoot the Check Engine Light for Free

Even if you find a good mechanic, if you’re like me, you shiver at the thought of paying hundreds of dollars for major vehicle repairs. Well, the dreaded ‘service engine’ or ‘check engine’ light came on in our Pontiac Grand Am this past week. Even more, you dread paying $100 just to have your mechanic take a peek at your vehicle to tell you that nothing is wrong with it – but that’s what you get for being a responsible auto-owner. Or is it?

There is an alternative to those annoying ‘take a peek at it’ vehicle labor expenses. And it costs nothing. The service engine light comes on in your vehicle because the computer has diagnosed that something ain’t quite right. When the light comes on, a code is stored as the reason for triggering the light. When you take your car in to get it checked out, the mechanic hooks up a little diagnostic computer to your vehicle’s computer. They will then get a code and description that tells them what the issue is.

OBD-II: A Background on Auto Diagnostic Codes

Every vehicle recently sold in the United States has an onboard diagnostic system that self-diagnoses a variety of vehicle issues through the vehicle’s diagnostic computer. The connector to this diagnostic system is called OBD-II (on-board diagnostic, version 2) and it is standardized for every vehicle sold in the US, 1996 and newer. When your on-board computer detects a problem, it outputs a code through the output, and the code can be read by an OBD-II code scanner, or reader.

OBD-II codes, or PID’s can help diagnose powertrain, emission, and other vehicle issues when diagnostic readings are out of accepted ranges. You can find a list of OBD-II PID’s here.

Check Engine Light: The Mechanics Dirty Little Secret

check-engine-lightWhat your mechanic probably won’t tell you is that you really didn’t need to shell out $100 just for them to hook up an OBD-II scanner to check on the service engine light. You can get that for free at most auto-parts stores. I’ve had this done at Napa and Advance Auto Parts. It costs nothing. The auto part stores carry these to cater to DIY’ers in hopes that they, in turn, buy the auto parts at their store to make the fix on their own. It takes them 1 minute to do this.

I was relieved to find out that the cause for the light to go on in my car was a possible vapor leak coming from my gas cap, caused by a weak spring in the cap. The gas cap costs $10. The store can also reset the computer so that if the problem persists, the light will come on again. If it doesn’t, problem fixed.

There probably are some honest mechanics out there who won’t charge you for this. But good luck finding one (perhaps, asking if they offer a free check engine light scan and their response is a good measuring stick for an honest mechanic).

Get your Own OBD-II Scanner

If you want to take things yet a step further and not go to the auto parts store every time, you can purchase your own OBD-II scanner. Here’s a very well rated OBD-II scanner for just $15. And there’s a bluetooth-enabled OBD-II scanner for just $22. That’s one-fifth what mechanics will charge for JUST ONE CHECK! Both of these scanners will give you a description/meaning, along with the actual code number. Very easy.

Oh – another thing – replace your car’s air filter on your own – it’s easy, and will save you a lot of money versus having a mechanic do it.

Check Engine Light Discussion:

  • What clever techniques have you used to avoid vehicle service fees?
  • How much were you charged to have your car ‘looked at’?

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About the Author
I am G.E. Miller, & this is my story. My goal is financial independence ASAP. If you share that goal, join me & 10,000+ others by getting FREE email updates. You can also explore every post I have written, in order.

  • Do You Dave Ramsey? says:

    Great piece of advice, thanks for sharing!

    • Cyndi says:

      I’ve owned an automotive repair shop for almost 30 years, The first thing we check is the gas cap, and there is no charge for that!
      Another thing you need to think about is Napa and Advance use a cheap little scanner, it might get you in the ball park what is wrong with your car, and you can buy parts from them,But as I have found it works sometimes , and the other you’ve bought parts that aren’t the problem. Not all Automotive shops are rip offs! My business is in the Small town of Williston Florida, we put out 25-30 cars a day and do no advertising, it all word of mouth.

      • Dean Reynolds says:

        Thanks for your straightforward answer and honesty.

      • lisa says:

        Hello, you seem like a person who is up front and honest, that is why I would like to ask you a question , and I hope you might be able to help, I bought a used car, I traded in mine ,and gave the guy cash, so all together I ended up paying like $5500, for a 1999 lexes, nice car motor is wonderful, but about 2 months down the road the check engine light when on , and so did the traction light, I went to see the guy I bought the car from , and he said oh it could be the cat. converter, and he said so what you have a sticker, and he laughed it off , and walked away , and I was like ok what about next year when I need a sticker, well come to find out there were so many hidden things wrong with the car, I also found out he unscrews the bulb for the check engine lights on some cars he sells. What can I do. I am a single mom with no money , and I told the guy that, I was like please this is all I have , and if there are things about this car please let me know, oh he swore it is beautiful, your going to love it. There was a rattle under the car I told him about right away, so he give 30 warranties and make an appointment like for the following week after I bought it it was like 8 days later, he did that for a reason didn’t he? Well he fixed it , but not really the problem was still there, I brought it back , but by then it was to late, Please tell me what can I do to some how recover from this. I do want to tell him what I know about the tricks he is pulling on people, and me. how long does it take for the check engine light to go on after you shut it off? Please if you can or anyone help me out, I would be very grateful for any help . Thank you for your time, and I look forward to hearing from you.
        Lisa From Mass

        • Summer Robinson says:

          If my check engine light came on and someone scanned it real quick and got a code would that tell me the problem with my car? Please help I dont have much money.

          • RL says:

            TAKE IT TO AUTO ZONE THEY DO A DIAGNOSTIC TEST FREE OF CHARGE.BEST OF LUCK. They will tell you what the repairs are and prices on parts if needed.

          • Charles says:

            Unfortunately auto parts store, have quit coding cars and will no longer turn the check engine light off. Guess someone screwed up. So now… We are ALL back to paying for a full diagnostic when this happens. BTW my light is on… Still driving.

        • Shareah says:

          I don’t mean to be rude, but may I ask what a single mother with little money was doing buying a lexus?
          If you don’t have money to begin with, don’t buy a luxury car! With that money, you could have found a newer car with probably less miles that would be cheaper to fix.

          That being said, look up the lemon laws for your state.

          • Tiffany Coker says:

            That was an extremely rude and judgmental statement.

          • Trey says:

            Shareah nailed it on the head, if your that broke you shouldnt have bought something like that.

          • Rene Provencher says:

            You guys may realize that this Lexus was more then likely a great deal. How do you know how much she paid for it? Generalizing is an ignorant reply to someones problem. She wanted a car that was a good vehicle.

          • Sharon says:

            It never ceases to amaze me how rude people can be when another person is asking for help. Not just the above comment, I’ve seen worse on line. When someone’s asking for help and they’re in a jam, you probably only make them feel worse. One word, KARMA!

          • bear says:

            It’s not rude nor is it judgemental you all. A luxury car is just that, a luxury. Expensive as all get out when they break. A 90s sedan or SUV would have been far more cost effective to maintain and would have been something that could have been easily modified to fit different tastes.

          • Seamus says:

            There’s no such thing as a good deal on a luxury car. If the average market value on a car is $10000 and you get one for $8000, be prepared to put in an extra $2000 to get it reliable. A good early 2000’s Honda civic or Toyota corolla has a low value and low repair cost and are usually owned by adults.
            I just recently bought an Audi TT for a very low price, but I’ve since had to replace the suspension ($1500), new tires ($600), and I’m currently messing around with figuring out the codes it’s giving me.
            I can tell you from experience you’re never going to get a good deal from any dealer or private seller. They’re looking to get the most out of their sale, and if they are asking less than average there is a reason.

          • wc says:

            God forbid an unwed mother driving a 10 year old lexus.
            Im a certified buttwiper I guess I shouldnt still be rolling in my 21 year old cadillac that I have had for 8 years! Hey its paid for & it paid its dues. Perhaps this lady should have got a 2 door cavalier with manual transmission & hand crank windows:) Thats what I used to have. Was the cheapest car I ever run!

          • TYPE O NEGATIVE says:

            It’s a 15 year old car, dingleberry

          • Sheryl says:

            No, it’s not rude, it’s common sense. Any luxury car is very expensive to repair when things go wrong.

          • Darlene Scott says:

            Doesn’t matter what kind of car, they will still try and cheat you. I am just pissed at them taking a woman for granted, thinking we don’t know about cars. My Sevice Engine Soon Light is on, took it for inspection and Minike tried to pull everything under the sun on my inspection. I have a 2003 Grand Am. Have took it different places and got l00 different answers. It reads oxygen sensors, but they can’t be sure, because they want me to pay 150.00 to hook it up to the diagnostic machine, Because the OB scanner code may not be right. BUT a 150.00 diagnostic check will tell me. And that’s after going to 5 shops. I guess I got stupid on my head. Now I got to pay for my taxes being late because I don’t want to be cheated from people who are suppose to do the right business thing. Oh and when I brought it the dealer also tried to cheat me, but GOD took care of him and he ended up fixing my car.

        • ruth knight says:

          Go to your news media explain what happened I don’t think they want that kind of public knowledge.if u try that email me back.

        • gary says:

          Its your brake fluid lvl

        • Linda Combs says:

          I have taken several mechanics to task by reporting them to the Bureau of Auto Repair. An inspector goes to the mechanic and determines if he was at fault Twice I was refunded my money because of fraud by the mechanic

        • Linda says:

          Hi my name is Linda and I have a problem that’s very similar to what you went through Lisa. Over a year ago I purchased a Chrysler 300 from a dealership it was finance for me through a bank for $16,000 and course I had some problems with it I think I’ve paid a total of $400 for repair since I bought it. A couple weeks ago I tried to get it inspected because inspection is due now and Mechanic tells me that my engine light should be on. He thought it was blowed out. Then I took it to the Chrysler dealership to have it checked and they found black tape covering the engine light!!I was in disbelief, I am livid that they would do something like that!!So when it comes down to it what car someone choose to buy is really their business but when someone does something illegal like that, that’s when it becomes a Criminal Offense. This exactly what this man did to you!!! I’m not a single mom I’m a married woman of 18yrs w/three kids but what difference does that make, “RIGHT”!! I am NOT taking it lightly that someone did this to me I have went to the bank that finance my vehicle,I sent messages to the Better Business Bureau,I’ve called the Action News Jason Stougenke to blow the whistle and I’m reporting it to the DMV he will not get away with this!!!! I know it’s been a long time since this happened to you but it really touch my heart to see how people can judge you about what kind of car you bought but if they had READ FULL STATEMENT of what you had said they would have seen this was not so cut and dry!! I hope that things have worked out for you since you posted this! Believe me God is going to take care of the man who did this to you!!I Pray that things are well with you and your children and that you are in a better place with your vehicle!! God bless you and your family!! Sincerely a Sister in Christ, LOVEO:-)

        • proMobile Diagnostics says:

          When you buy a used car it is pretty much buyer beware. When you buy an “as is” car most states have laws to protect the dealers. Your best bet it to try and get him to pay half or some of the repairs. Good luck. I run into this all the time.

      • Shirley Mckeen says:

        Thank you so much for this tip. My gas cap is loose light came on. Then my check engine soon light. Going to check my gas cap. You may have saved me $$$!

      • LHarper says:

        I own a 2001 Dodge Intrepid. You can pull your codes very simply. I’ve attached a link below. Each time mine has always been the same code which has always came back to the gas cap.
        Here in NC a yearly inspection is required so the dreaded engine light can really be a nuisance when it comes on right before inspection is due. I have learned a lot from the Dodge forum and that is how I found out about pulling the codes myself. The dealership will never tell you this. The very first time I had a check engine light come on…off I went to the dealership, and it was 75.00 just to have them pull code. Just trying to help someone else out. Owned my car for 12 years now and the check engine light I refer to now as the phantom light.

      • Patricia says:

        That’s right & for instance I drive an Acura & if I put after market parts in it, it definitely can damage something else! I have found that out the hard way! Never again. I only go to either the Acura or Honda dealership for parts and service.

      • d says:


        • w says:

          Sounds like a shit mechanic wanting more money. Yeah those scanners are cheap but they work. I wish everyone of you that act like this fall on hard times. Maybe like get assaulted by your wife. Daughter calls 911 and you get arrested. In 3 months get arrested, served with protection from abuse papers, get served divorce papers, and get laid of from your job. Yup I’m going to go to some asshole who charges $75 to plug in a code reader and turn a key on. You are not special enough to get paid that kind of money for less than 3 minutes work.

        • Ted says:

          BS…I checked…Napa used the EXACT same code reading device that my auto repair shop used.

          I took my vehicle to my mechanic (rated the best in the city)he read the code for free, (gas cap) reset the computer for free…same thing happened. he reset it again…checked the gas cap…set the gas cap in a certain position to see if someone was tampering with it…same thing happened again. no tampering. So I went to Napa, they coded it with the EXACT SAME CODE READER, it was the same code, gas cap, they reset it, so I purchased an OEM gas cap and the same thing is happening. took it to my mechanics shop and set up an appointment for Monday…could be a vapor vent tube leak, we’ll soon see.

          The point is…Reputable parts stores still will read codes for you FOR FREE. and reputable ones use the SAME DIAGNOSTIC CODE READERS as reputable shops. They know if they screw up you won’t come back.

      • Jim Jones says:

        Give me a break. Auto mechanics are the worst and they will never stop trying to justify charging people to use a TOOL that is needed for them to do their jobs, and there are plenty of other tools that they use that cost much more than a diagnostic reader. Do they charge a special fee to use any of the other tools? No. This tool takes the LEAST effort to use when compared to other tools, yet they want to charge people $100 to run a diagnostic test. It’s dishonest and just a way for mechanics to weasel as much money from you as they can.

    • david says:

      gas cap leaking… Yeah RIGHT

    • Summer Robinson says:

      If my check engine light came on and someone scanned it real quick and got a code would that tell me the problem with my car? Please help I dont have much money.

    • ruth knight says:

      Hi Dave
      I was one of the dealers suckers,I went in the dealer with three difrent diagnosis all calling for cylinder misfire on o2 which spelled out checking coil It also had blinking check engine light well the service manager passed me o another service rep wrote a repirepair ticket and told m to have a seat after arriving at the dealer at 1130 am got concerned what was happening he explained o m the next test would take another two hours he told me that the test first one would be 149.50 and it needed another test that took 2 hours that test would cost another 250.00 well I finally told him to return my car in condition that it came here he said OK his diagnosis was he Had to replace the engine he charged me 290.00 for that service I was sent home with my car running worst then it was when when I came out of the money when the car only had a slight idling problem and I asked him if he can check cylinder he said he did not get that reading it was calling for replacing the engine which was $2,560.00 and refused to have repairman test ride my car he said call him back I called him five blocks later he said that was how I brought in Iam 75 years old not in the mood for his bullshit when his boss returns I will call news media on him if I get no satisfaction from his boss.

  • SJ says:

    How uncanny to read this article considering i just came back from the Toyota dealership that gave me an estimate of $94 to run diagnostics on my car to figure out why the check engine light was on. To my luck i had gone to Sears Auto first that gave me the error code by running the quick diagnostic as your article lists, free of charge, which i then took to Toyota and didn’t pay a dime because it turned out to be a warranty issue!:) How often does that happen?!

    But the good thing about getting the error code was that i googled it before going to the dealer and had a pretty good idea of what the problem was and how much it would cost so that i could level head with the dealership instead of them taking advantage of me not knowing anything about cars and charging me a ridiculous amount.

    • LS says:

      FYI tried to take my car into Sears and they said it cost $100 to diagnose and they do not do work on it if there is something wrong

    • Shareah says:

      You’re the type of person us dealerships hate. You come in thinking you know what’s wrong with your car, assuming we are going to scam you, and make a huge stink. Just because Martha Sue had one issue doesn’t mean your car has the same. For something like a check engine light, the proper diagnostics must be run to be 100% sure what is wrong. Would you go to your doctor, after Googling your symptoms, and demand that he give you medicine because that’s what you saw online? Skip the x-rays or MRI because you saw something online? I understand diagnostics can be expensive, but it may save you money in the long run. Find a dealership or mechanic you trust.

      Also, check your warranty… this is something you can Google. Don’t bother running around town when your car is still under bumper to bumper warranty!!

      • Tiffany Coker says:

        Well, that is because you often do. I paid $125 last year because my car’s service engine light came on. The dealership claimed that they knew what the issue was after me paying that much for extensive diagnostics. Then I paid another $90, was called to go pick my car, was told it was fixed, got half way home and the light came back on, took my car to a mom and pop service place the next day, was told it was simply a fuse needing to be replaced, replace it and bam no more problem. So yes it is wise for people to have a little knowledge about their own vehicle so that they can avoid wasting hundreds of dollars they don’t have.

      • tommy says:

        you are a bullsh.,#$ you must be a mechanic! so stop your bs and start being honest if you can, i doubt it!!!!!!

      • Brian says:

        Your the first service person at a dealership that has stated this, every dealership I have used has charged for the diagnostic even when its under the so called bumper to bumper warranty, in fact Mercedes dealership charged for diagnostic even with extended warranty and factory and then tried to say that the SRS light was on because the seat belt sensor was bad and they considered it abuse because it was corroded on the circut board in the sensor, when you look on the internet you see this is a ongoing problem for mercedes, so please don’t try and say the dealerships will doagnose it for free if its under factory warranty cause they won’t they will make you sign something that says they are going to chrage you a certain amount and then if they find its under warranty they will reimburse you but usualy try to state its not covered, if its a service engine light its most likely not abuse but more likely a sensor bad part or even a loose gas cap.

  • Jen says:

    Coming from a family of mechanics, while this could be a good place to start, I wouldn’t rely on those stores to have the most up to date diagnostic equipment. The only places that have those are car dealerships as they are quite expensive and they have to pay all update patches. Just keep in mind there are many reasons why things pay more. I think SJ had a good strategy.

    • Berneice says:

      I just paid 120.00 at a dealership for diagnostic and over 500.00 total with 300.00 for labor. Said they charged me for 2 1/2 hours labor when the car wasn’t in their shop 2 hours total. Installed evap vent solenoid. Harness trans cooler lines. I reads ally feel that they are overcharging. 120.00 to diagnose seem high too. I told them I felt it high. I won’t be going back there for more than oil change.

  • Britt (Your Roth IRA) says:

    Great idea! I did not know this. I’ll have to pass this information along, and I’ll probably go check it out next time I go to fix something myself at AutoZone or Advanced.

    Luckily, I’ve actually found one of those “one in a million” honest mechanics. Last year, the air conditioning went out in my 1994 Mustang. I took it in fully expecting a $400-$500 repair bill…

    The final cost?


    A vacuum tube in the switch broke. The mechanic charged $8 for the part and $0 for the labor.

    Now that’s a smart mechanic! (Of course, he’s local and not part of a major chain)

    Because he does things like this on a regular basis, I always take my car to him first. When something is expensive, I trust he’s telling me the truth…

    • ruth knight says:

      Yeah you caught a break

    • Fred says:

      Yeah, he’s a real smart mechanic. Gonna go far not charging for his work. I don’t do anything for free. Do you go to your job and work for nothing? All you cheapskates need to start walking. Does the grocery store give you free toilet paper?

      • Mona says:

        Yeah, Fred, you’re the kind of money-grubbing dirtbag that give mechanics a BAD reputation. I guess you haven’t figured it out that when a customer needs a quick diag or help with something simple and the mechanic fixes it at “no charge”, this instills TRUST and DECENCY between the customer and the mechanic. DECENCY brings the customer back; TRUST will keep the relationship going. Gawd, people like you make my bu++ tired…

        • RSMAsON says:

          I am one of those local mechanics I don’t charge for any brake job due to my wife and kids. HOW CAN YOU PUT A COST OF LABOR TO HELP PROTECT SOMEONES LIFE we decide we could not so brake jobs a labor free. I always have return business due to the respect and trust this helps me start with anyone

  • Andrea (Recession Proof Living) says:

    Great tip! I hate all the fancy computer diagnostics that cost a fortune to get checked.

  • Craig says:

    My car recently has its service engine light go on and I could tell something was wrong with the car, but didn’t want to take it in and spend hundreds. I waited a few days and the light went off and things were smooth. Still prob should get it looked at, like your advice, will def help.

    • ruth knight says:

      Yes get proper credentials of person doing it I went o a deaeler and got a swift kick please beware I also had a check engine light turns out making a fool of me out of $290.00 car running worst then when went in be careull ask a lot of questions if it don’t sound right get the heck out of there.

  • Joe Attardi says:

    Sometimes you can diagnose it on your own, with no special equipment needed. Back in the day, my ’94 Toyota Paseo’s CHECK ENGINE light came on. I did a little research and found out that there was an alternate way to get the diagnostic code (not sure how widespread this is)…

    I simply had to short together two pins of the OBD connector with a paper clip, and turn my car on. When these two pins are shorted, the CHECK ENGINE light flashes with a certain pattern that will tell you the code.

  • stephanie says:

    I used to have a 92 Ford Escort, and the check engine light came on any time we drove the car over about 50 miles per hour. We learned to ignore it. I now have an 02 Ford Escort and the check engine light has been on for about 3 years. I’ve had the car serviced multiple times in the past few years, and they’ve never mentioned any problems with my car that would cause the service engine light to be on. My car runs beautifully. I wouldn’t worry about a service engine light unless there’s some indication (other than just the light) that something is wrong with the car, especially if you get your car serviced regularly anyway.

    Also, I’ve discovered that a lot of times places that do 15 minutes oil changes will check out other stuff for free if there’s something you’re concerned about.

  • Phinance says:

    Thanks for sharing! I know nothing about cars, but it’s interesting that the car computer records these errors. Cars should come equipped with their own diagnostic tools to let people know what’s wrong with them. This has to be a car industry secret type thing.

  • Chris says:

    The $100.00 dollar code-read is a monster rip-off. I seem to ALWAYS have an engine light on in my truck so I finally bought a little OBD-II reader (costs half of a single “diagnostic” at the Ford Stealership) and its easier to use than a cell phone. Takes about 10 seconds from the driver seat.

    I just have HAD IT with paying hundreds of dollars to get a good running vehicle thru state inspection. I’m going to learn a bit of mechanic-ing. But don’t kid yourself, there are hundreds of possible codes and its not always as simple as a gas cap.

    Empower yourself and learn something about your car – it will pay off hugely in the long run.

  • Justin says:

    Great advice. Also, for the $100 they would like to charge you to check, you could buy your own cheaper model of scanner. Thanks for sharing about the free diagnostic check at your local auto parts shop.

  • Little House Jay says:

    To be honest as much as I dislike the charge (about £100 not $100) to hook the diagnostics up and tell me weather it’s a minor thing or indeed not. MY SLK cost enough to put up with this to be frank.


  • Auto Repair Joe says:

    Most likely your light isn’t on because of a “glitch.” The vehicle monitoring system is extremely reliable and stable.

  • Amanda says:

    I love this tip! What a good first place to start. Of course your auto manual tells you that the warning light is the first indication that something may be wrong and having it fixed now could save you money down the road – but that diagnostic fee has always made me hesitant. Will try it out the next time and hoping there is not a next time!

  • Rick says:

    When a check engine light triggers in a car it is telling you that their is a fault in the operation of your vehicle. The ability one may have to scan a vehicle for codes does not mean that one has the ability to repair the vehicle. The code that you retrieve does not give you a slam dunk and tell you how to fix the car, the code allows you to digest faults associated with a particular code. It still requires a certain level of automotive skill to be able to repair the vehicle once you have determined what is actually wrong.In other words just because you have a little information about your car does not mean that you know what to do with it. Yes there are some codes that will trigger that are minor however this is not true for all check engine light problems. Todays cars are extremely complex, a wrong diagnosis can send you into a frenzy of parts purchasing that may or may not fix your problem while a correct diagnosis by a competent skilled technician will save you money in the long run. As a mechanic with 25 years in the service business I am here to tell you, it is not always as simple as buying some cheepo $50.00 tool from one of the local parts houses and even if you are able to retrieve the code the chances of anyone being able to provide you with the proper diagnosis from the parts house that you bought that cheepo code reader from is pretty rare. Good luck if thats how you want to go about repairing your car. Guessing is no substitute for experience, so do yourself a favor take your car to a trained technician and pay for the appropriate amount of time necessary to get a proper diagnosis and your car fixed right. You pay your doctor for his time and education why not your mechanic as well.

    • Anthony says:

      I’m with this guy.

    • Larry says:

      You’re right on the money with your comments. Just getting a FREE trouble code check only tells you what kind of problem you have but not actually what exact problem you have. Trouble codes need to be PINPOINT TESTED to verify the exact problem. It is often a very complex procedure and time consuming. That is why most all repair shops charge for that time spent on your problem. Average price for this is usually around $80 to $120 depending on where you live. So just bite the bullet and pay these technicians to work on your car.

    • Spencer says:

      Completely agree. a P0300 code means random misfire. So what is wrong??? No freaking clue. You’ve got to test plugs, wires, coil (s), So many things that could cause that one code. So pay a mechanic and stop throwing parts at it.

    • al says:

      I know where you are coming from..You are a mechanic and you have an inside knowledge of what is wrong and how to repair your car..what about the rest of us who had been ripped off by some greedy and dishonest so called mechanics (technician). I had my car recently repaired and all belts replaced.When I picked up my vehicle and brought it to a shop to be smogged ,it failed.There was an error but no code showing, The technician told me to drive the car around and put at least 200-300 miles on it since there were work done on the engine, which I did and when he checked the code came up and he told me there was a problem with the EGR..I went back to the mechanic who fix n my car but he told me the problem was the knock sensor that the smog technician say it was not.My soon to be ex mechanic tried to charge me for the sensor $365 for parts and $600 for labor after I shelled out $1800 for fixing both cylinder heads of my 99 Mercury Villager.So a little head start on our vehicle will help us an inside tip of actually what’s wrong with car..This is not necessarily amount to fixing them..I went to grade school just to learn the basics not to go and teach afterwards..A little understanding of stuffs gives us a better defense against dishonest mechanic and there are LOTS of THEM!!

    • ljem says:

      ya just like my bb did and $800.00 later the light is still on
      ok take to a knowledgeable mechanics and get $40.00 & 80.00 parts put on for the price of new rims and tires lmaoX2 oh ya not ripped off ok seams a little out outrageous and don t forget all the other things they will find that need repaired soon if not now like 5 year old struts ya my cars 13 years old and i ve had older that never needed struts
      good luck with that

    • ruth knight says:

      I had three diagnosis from three different scanners went o dealer I bought car from was not interested in repairing more like replacing the whole engine for a lot of money.

    • Dan Wilson says:

      I can answer the” You pay your doctor, why not pay your mechanic” question real easy. it’s easy to find and honest doctor.

  • Marcus Bethea says:

    I have been doing this for years. It is sad because they don’t offer this any more. Now you go in and the tell you they cant any more. Used to be you just give them your id and they let you borrow the tool. Some told you what the problem is some just gave you a code. You write down the code and look it up online. Now they want you to buy the portable machine. which isn’t bad for 50 to 100 dollars if you are a DIYer

  • JoeD says:

    The first and best thing to do is disconnect the negative battery cable and leave it off for 30 seconds or so, while it is off tighten your gas cap, then reinstall the cable. This allows the on-board computer to reset and will make the check engine light go off. Then run your car normally, if the light comes back there is really a fault, otherwise it was probably a loose gas cap or phantom fault.

    I agree with Rick above, to just start replacing sensors based on the codes can quickly get very expensive. It is better to go to a mechanic who will actually find and repair the problem at the outset.

  • Ron Ablang says:

    I’m surprised that no one here mentioned that you have to have a car that is fairly recent (don’t ask me when) to be able to hook up one of those diagnostic readers.

    I have an ’88 and ’90 vehicles, and they probably won’t work for this stuff.

  • Salman says:

    1996-Present = ODBII System (You need a diagnostic computer to read codes)

    Prior to 1996, you only needed to jump two connectors to send the car into diagnostic mode while turning the key to read the code on instrument panel.

    The location of the connector varies from car to car. In the early Toyotas the connector was around the engine compartment. On the early Hondas, the connector was located under the passenger side dash.

  • David says:

    If your shop is doing its job it will scan all modules for faults and softwear updates.This will give you the whole picture of your vehicles module network.We offer this for $80.00.We use oem scaners for most all car lines.

  • Mike says:

    What can you do when the shop diagnose a check engine fault that is incorrect while charging you over $500.00 for work done and sensors replaced? Light returned following day.

  • Cat says:

    Coming from personal experience, there are many ways a person can go wrong with these free check engine light tests. I took my car to a friend’s husband who supposedly has been fixing cars since he was small. He supposedly went to school too, though I found out later it was for Harley repairs and he quit when the instructor demanded he take out his piercings if he wanted to continue his education there. He decided to drop out.

    Nevertheless, I took my truck to him, trusting he knew what he was doing, and watched him use one of these little hand hold code scanners that you plug into the car. He said I “probably” needed a new O2 Sensor. Well, he installed that cheaply enough and two days later the check engine light came back on.

    Do you think I am going to go back to him so he can change out yet another part that might not be problem? I told him I could get one of these free check engine tests to save him the trouble, but he said all they do is try to tell you need this, that, and the other thing – that you may not need. Well guess what? I feel he did the same to me.

    Rather than go back there, I called my regular mechanic and he said that is what happens you throw part after part at the problem and can waste money that way. Those smaller, less sophisticated diagnostics only spit out trouble codes and one trouble code could mean multiple problems.

    Places like Pep Boys count on that. So I am going to get a proper diagnosis to know EXACTLY what the problem is and that it can be fixed. Check engine lights can mean serious things – too serious to leave to chance. I am not going back to this hack for anything other than minor, easy to fix problems.

  • Kacie says:

    My check engine light has been on and off for a year and a half. Ive been told that it is an 02 sensor awhile ago, no money to fix it. Ive been running ARCO gas in my car. Seemed always to be fine. But I heard recently that Chevron was better and on my first tank last week, after driving 20 miles that light has gone off and stayed off. Is this a fluke or does it have to do with running better gas in my car?

    • Roland says:

      Kacie ,, i had the same on nissan sentra 1.8 ltr 2002
      came on off some time turning a uturn to fast the light came on then went off stayed on for 1 day and as mucha s 2 weeks then i turned the engine on in the morning and simultanesly turned on my garden hose with showerhead whille engine runnnig it keept engine longer cool thsia must have cleaned out some airflow or othe r glooged valve now driven 80 000 miles and it never came back on again it si a p*** the diagnistic is a money making crap nothing to do with passing the car in test,,
      regards roland

    • Roland says:

      the new mercedes have now 12 PC on board each talkinbg to one an other the owner will pay what ever a mech tellls them is wrong. seen to much rip off and the engine light is the biggest rip off, like isaid if a simple oring or presure cap is leaking that should be made readable on the dashboard for a consumer to read, and not some pc odbii reader,
      to the guy that said we pay doctors go and read once what they get ,for diagnostic check the bill the doctor get from insurance companie and wha t he //she gets. you may consider to be well overpaid, specially when we have to come back in a week then told well something else gone wrong, with the reader they can reset the engine light will go off and stay off till a fume is acumalting again ,, right u guys are ovedr paid and have mostly no idea, ((( could but many dif things great diagn,,,,,, bye for now

    • jeanne says:

      I quit using a arco gas a while ago and I believe my car runs best w chevronm

  • Roland says:

    tO YOU MY FRIEND ((( Rick says:

    October 30, 2009 at 3:00 pm )))


    would u agree that the check engine l should be a serious matter and a Gas Cap not locked or has gasket leak that should show in your dash board, what check gascap or like we have it on the brakes brake sensor,

    Now to your so called educated mechanic he wanted to take engine head of and clean it ,, iwent home in july and the next morning i got up started car and use a gentle shower sprayer garden hose
    then let the car run for an other 1 miinute and then turn it off

    went to work light wa no loner on and since then i drove car 80 000 miles so much for that,
    i think regardless of new price if they all use ODBII system reader it should also includ a owners info what could be wrong a gasket on a oiltippin stick or intake air flow thyeh are s narrow so why then build something and have owner spend money on stuff the PC does not tell them or the costumer ?>???

    i think that is a rip of from dot not passing the car when they can not diagnose quickly
    heere you say it can be this abnd that if the codse has several meaning that is not a code reader that is guessing okay,

    why should the car not pass test just because the gascap is leaking fumes,???

    while i see cars parked leaking engine oil or transmission, fluid which then makes the blacktop to disintegrate okay

    and i am not angry just amassed at some dumm remarks here,



  • Mike says:

    I have read a few comments on here and other sites too. People are tired of being ripped off by shops and dealerships and paying over $100 for them to just scan to see why there engine light is on. If there was a business out there that offered to scan or turn off your engine light and give you the codes to and what is wrong with it for only $15 to $20 and they came to you. Would you call them?

  • Nk says:

    Wow…great advise, they usually charge us $89 at the dealership to diagnose the problem and $49 at Firestone but one good thing about Firestone is that they will wave the diagnose fee if you get your vehicle fix there and the dealership wouldn’t. Thank you so much!

  • Susan says:

    I recently purchased a 2004 Kia Spectra, four days after I had it, the car jolted slightly and the check engine light came on. I took it to Auto Zone and they did the free diagonstics on it, and code p1529 came up, which they told me was a transmission sensor. The place I bought it from sent me to “their” mechanic. I only had the car less that a week. He took it for a test drive and could not find the problem so he said. It stopped because he cleared the codes, and 3 days later it was on again and the car jolted slightly. They came and left me a loaner, took the car and brought it back the next day saying it was fixed. And again, 3 days later, the light came on again. I don’t know what to do anymore, the light does go off on occasion, but does come back on. The tacometer and speedometer are both functioning properly so I know its not a speed sensor.

    • Brenda says:

      So-called certified mechanic charged me $550 to replace upper and lower intake gasket, oil change, coolant system flush , reset engine light. 5 mile down the road , van stalled , rough iddling when cooled down , now this , b#^{}*+# has the nerve to tell me that I probably oxygen sensors or there might be something else wrong.

  • Tara says:

    O’ Riley’s does free diagnostic tests also.

  • Bobby says:

    I use to take in my old car to the shop all the time and it would cost me $40 for them to scan my engine light and an other $25 to turn it off a total of $65 for both. I got sick of it and found a person that started a business Scanning and turning off engine lights for $15 total for both in Coquitlam. He was half the price of what a shop would charge. He will give you the code and what is wrong with it. Try craigslist and you will find a few people that offer it.

    If you wont to know more about it you can email me:

  • koko says:

    I had my car scanned at autozone today, and while it’s a nice service, it gave me only an overall description of what was going wrong with my car (cylinder misfire) and a list of about seven things which may be causing that to happen. So to fix it myself, Id have to buy and replace all kinds of parts to figure out which one is faulty. Could get pricey…. what I’d like to know is, how much more sophisticated are scanners at the shop or dealership, and how do mechanics go about troubleshooting these kinds of problems? Is it all just a guessing game in the end?

    • matt says:

      No, it is not supposed to be a guessing game. However, many mechanics lack the skills to diagnose even with the proper tools, so they just swap parts. To diagnose a cylinder misfire. I would check for cosistent spark, check for proper operation of the fuel injector, and if those were operating I would check for a mechanical issue in the affected cylinder. I would not use a scan tool for these tests. I would use various diagnostic tools. Digital multimeter, mechanics stethoscope,noid light,spark tester,test light,vaccuum gauge,compression gauge,fuel pressure gauge, fused jumper wires may all be needed to diagnose a misfire. As well as service information such as a wiring diagram and component locator. A REAl scan tool may display misfire counts to suggest which cylinder is misfiring, but aside from that it is about basic automotive test tools and REAL troubleshooting skills to diagnose a misfire. The free code scans are just an attempt to sell parts. Some problems are simple and can be found by scanning for codes, but others require real skills and equipment.

    • Jason says:

      I’ve been a full time tech for 15 years. You are right about them giving you a list of ‘could be’ items. I like testing or ways to prove without costing the customer much money. If the misfire code was for a paticular cylinder then you can try moving the spark plug to another cylinder and see if the code follows the new location. If it is “Coil Over Plug” you can swap coils from another cylinder. This doesn’t require buying anything & can be done in a few minutes. If those fail, then you need to determine if it is an engine mechanical failure (compression), ignition failure (no spark / weak, etc) or fuel.

      That is why real shops will cost you some money to DIAGNOSE. It could be anything form weak compression to a shorted fuel injector. At that point you find the most logical test and start testing. But in some cases you could require a cheap $5 volt meter to a couple thousand dollar lab scope.

      Some shops will start with a tune-up. While this *could* fix it, but what happens if it doesn’t? Will that shop bill you for it? Those are the kind of questions people need to ask.

      At our shop if I tell you a tune-up will fix it & it doesn’t – YOU DON’T PAY. That holds me accountable for what I say.

      If the shop says this part failed, and you ask them to show you how they came to that with test results and they stumble – walk away. Fixing cars isn’t cheap for the consumer or the shop.

  • Ric says:

    You guys NEED to get an app for Android phones called Torque. It gives you the engine codes and clears them. The app cost 5 bucks and you will also need a bluetooth OBD2 connector for 20 bucks ( Ebay. ) I put my service on craigslist for 10 dollars to read and clear codes. I do about 30 a week. Not bad considering it takes 5 mins per car. I just saved you guys hundreds of dollars. You’re welcome.

  • STEVE says:


  • yanualia sellers says:

    help me please, my engine light came on and it won’t turn off, i got a 2002 cadilac deville, please help me, the light wasn’t on before, what happened is that i was listening to music for a long time and my car battery became so low, so i called my insurance to help me and send me the tow guy to charge my battery and then after my battery was charged the service engine light came on, and never turned off, please help me, what should i do .

  • RJ says:


    • Nick says:

      If it takes 2 hours to diagnose the problem then charge for 2 hours if it takes 5 minutes to diagnose then charge for $86/12=$7.17 but you will not do that will you? And to be paid to reset the code and screw on a gas cap $86 is a ripoff anyway you look at it.

      • matt says:

        well if it takes all day you still only pay $90. If they charged by the hour and it took 3 hours to diagnose a tough problem and the shop charged $80 an hour that would be $240 just to diagnose. Then you complain that you paid $240 just to have them “look at it” as people say. They make money on flat rate, and they lose money on flat rate.

    • al says:

      RJ, some mechanics needs to be slammed..Yes,you bought all those expensive tools and equipments for your shop..I know some of them pay installments on these tools. If you do a good and honest enough job it is well and dandy..Fools like us who does not know A to Z on cars are the easiest VICTIMS of dishonest mechanics..They doesn’t seem to care as long as they can pay off their EXPENSIVE TOOLS at their (VICTIMS) err customers expense.I do not mean to imply that all mechanics are scam artist but I’ve been around too long to have seen them.Help your customers and they will turn around and give you free ads by word of mouth and praises.In closing MECHANICS NEEDS THESE TOOLS!!!!as much as WE NEED OUR VEHICLES to get to and from our jobs to pay for whatever expense our trusted vehicle will incur for us..I do need a mechanic whatever.

  • Laurie says:

    My friend is a mechanic and he will often charge a diagnostic fee when someone brings in an automobile. I hardly think this means he is dishonest as the article suggests. It isn’t always as simple as hooking up the computer to the car. The code will appear, but there can be several different problems related to this code. The code gives him a place to start. He then digs in to figure out exactly what the problem is and it usually takes more than five minutes.

    Spending time figuring out the problem on someone’s car, so the person can then go and buy the parts at an automotive store and attempt the repair on their own, does not pay his bills. Diagnosing problems takes him away from the repair jobs he has in which the customer will be paying for his service.

    What surprises me is how many people will go to a doctor and pay for all types of expensive diagnotic tests without blinking an eye. Often these tests are inconclusive, so the doctor orders more tests and the patient pays for the next set of tests without a complaint or question. How many people pay for a round of antibiotics, only to find they don’t work and have to buy a different type? Do these people call the doctor dishonest?

    I think mechanics get a bad rap as being dishonest. Yes, there are some bad ones out there, just as there are with all service jobs. But this is not the standard. To suggest the mechanic shouldn’t charge for their time when you plan to then shop around the repair charge or do the job yourself is unfair. In my opinion, those that do this are the ones who are dishonest.

    • Brenda says:

      Some mechanics know what the codes are to turn off engines lights but they choose to be greedy and squeeze. As much money out of customers as possible there are no honest mechanics they all are crooks

  • KIm Kramer says:

    I have a 2002 Toyota 4-runner sports edition. Runs beautifully and always has but at the 50,000 mark the engine light came on.
    At that time I did take it to the dealership to get the light turned off. They charged me around $150 and explained it away as an o2 sensor problem, Again at the 100,000 mile mark, and I mean exactly- guess what the light came on again. Know what? I’ve had that light on, for over 70,000 miles now and I don’t care. Toyota told me they wanted $300 to turn it off. They’ll never, NEVER get my money for that again. One time was enough for me to learn this is a money making deal for the dealerships and car manufacturers.

  • James says:

    I myself would like to trust most mechanics but since they are in the business to make money you have your work cut out for you if you know very little about cars. A supposedly Christian mechanic wanted to charge me for a new transmission when all that was wrong was a 30 dollar speed sensor. I drove the car home in limp mode. Was about to take the transmission out to work on it when some guy walked up into my yard and asked if he could help. Thank God he did! He knew a guy who owned a transmission shop for years. The guy told me to replace the sensor and bingo it was working fine. Saved over 2,000 dollars. Getting a code and researching will give you some confidence when dealing with mechanics. If you find one you can trust then give him your business and referrals. Like my transmission issue I knew it was not gone because I was the only owner and driver and it just wouldn’t shift into a higher gear. Common sense was telling me that it had to be electrical and not mechanical. You have mechanical issues with a tranny you will know it while driving it.

  • Scott says:

    This author must not value a professionals time, knowledge, and experience. I assume if a plumber came to his house he wouldn’t want to pay them for their time either. Getting the code out of the computer is the easy part. It then comes into time knowledge and experience that helps PROFESSIONAL technicians to determine the cause of the fault code correctly the first time. Not guessing and installing parts and if the “light doesn’t come back on problem solved.” If you build a relationship with the technician that services your vehicle like you would your doctor, they won’t charge you for diagnosing simple solutions like gas caps, however when there is a difficult code with multiple possibilities there would need to be a charge to pay for the expensive professional grade scan tools that we need to use and the training that we need to attend on how the ever changing technologies in new cars are evolving. You probably try to diagnose your own health issues too and do not value your doctor either. good luck with that one!

    • Brenda says:

      To you Scott when doctor diagnose the patient if they’re not sure about the cause ,they don’t charging you, but send you to a specialist who can

      • John says:

        To Brenda’s response:

        That statement about doctors not charging when they are not sure of the issue is absolutely not true. BEFORE a doctor sends you to a specialist, you typically go into to see your PCP (primary care physician), and from that appointment with your PCP, he/she may refer you to a specialist. That appointment though, is 100% ALWAYS billed. Please let me know of a doctors office that does NOT bill for that appointment to tell you to go see a specialist. They simply do not exist. And it makes perfect sense that they do bill for that time because you are essentially paying for a their time, even if it is to tell you that they want to refer you to a specialist. Why should it be any different for an automotive technician? If you do not think you should pay for their time, why not fix the car yourself? You obviously can’t because you do not have the correct tools as well as the knowledge to do that.

  • ross rigoli says:

    ihave a2002 buick century,the check engine light came on.they checked it out with a smoke test machine.they saw where the smoke was coming so he order a part and installed it underneath the left back by the gas tank.then he said I have to drive it so that part they put in will have to reset it self.that has 3 weeks ago.he inspected my so my inspection runs. this month.he checks it with a meter and says I have keep driving it until it resets cost me so far $150.00.thats for inspection and the part and labor.

  • Catherine says:

    Hi everyone! I was wondering if anyone can help me.. We recently bought a used 2002 Nissan Altima with 2.5 engine for my step daughter.(100k miles )We ended up all the way in Yonkers to buy it from a private seller. The people seem to be nice, she test drive the car with her father. Everything seemed all okay, two days after buying the car check engine light turned on. She took it to the nearest mechanic,they told her that there are 4 type of computer sensor errors. The errors was NATS system anti theft system with 2 sensor, then the Emission, least but last heated oxygen sensors. The asking sale was $4500 but we managed to bring it down to 4k flat. The way it sounded we got scam, but whatever it maybe, the question is how much will it cost to have it all fix? Or anyone here has an idea what we should do with it… Thank you in advance….

  • LHarper says:

    I have a 2001 Dodge Intrepid. You can pull the error codes yourself by turning on and off quickly the ignition halfway twice..then turning it on one more time. The codes will appear on
    The odometer screen. I’ve dealt with thus for years and now call the check engine light the
    Phantom light. Car runs fine. The light recently was off for 5 weeks but came back on a few
    days ago. Interesting enough it’s due for emissions inspection the end of this month. So once again I will pull the codes and there always the same two. Drive it for 60 mikes after I reset the battery and then get inspection done. I’ve had this car for 12 years and hopefully will trade it in within a year or so or sell it. Waiting on a better paying job before either happens. I am in NC so the inspections are due annually as is property taxes. Ignore both and the State blocks you from renewing tag..

  • Nadine Garwitz says:

    It is my opinion that ‘engine light’ problems are like fingerprints. Every time it comes on the diagnoses is different. Never one is the same. My engine light comes on….I take my car to my mechanic…..I pay for the fix….I drive my car for a few weeks….the engine light comes on again….I take it back to my mechanic….he diagnoses it, ‘different problem’….he fixes it…..I pay the bill….next month same old engine light comes on….I take it to a different mechanic…he gives me a different diagnoses…I pay the bill…next few weeks same thing happens. After reading this, and all of the comments, I feel like I have really spent a lot of unecessary money getting the engine light fixed. From getting two new batteries up to getting my catalitic converter replaced. Tomorrow is Monday, and I am going to take my car back to my own mechanic with a printout of some of these comments. Then I’m going to the Chevrolet dealer where I bought my car and show them. One of the two places is going to fix my engine light for free or I’m going to start a campaign to try and stamp out this kind of scamming.

  • Tony says:

    I see a lot of back and forth on both sides beating around the bush. I don’t think any reasonable person thinks that a mechanic shouldn’t be reimbursed for their time and expertise.

    What I’m objecting to as a consumer is getting charged $125 because my check engine light came on, then charged $150 for the engine tune up (spark plugs, etc) and $50 for the oil change for a total of $325. That is gouging, plain and simple.

    I understand that if they simply tell a customer what needs to get done, the customer might choose to go somewhere cheaper or do it him/herself. It is reasonable to pay a fee for the mechanic’s time and investment in diagnostic equipment.

    But if I’m going to pay the mechanic to do the work, then I expect something different. I would expect that the mechanic recoups his/her investment in diagnostic equipment by adding a fraction in service charges or by adding a tiny diagnostic fee, perhaps $10 — but $125? That is 62.5% of the $200 parts/labor charge.

    Needless to say, I’ve subsequently taken my business elsewhere. Whether the new mechanic is any better or worse doesn’t change the fact that the other mechanic got my business once, but will never get it again.

  • Gerard says:

    To the author of this article. its published misinformation like this that gives auto mechanics a bad name. Obd1 & obd2 diagnostics can be difficult and aren’t something for amateurs. The comment about someone having a transmission code and trying a gas cap had me laughing though.

    *5 time ASE certified technician.

    • Alnthevalley says:

      I recently had the check engine light on and could not pass the smog if it wasn’t corrected. My smog guy hooked up the code reader which indicated an emission leak-fortunately it was just a loose gas cap-after it was reset at no charge, I drove it about 80 miles. Returned the next day and the check engine light did not turn back on-I passed my smog check and my smog guy charged me $40.00 total for smog check and certificate. I stop seeing my last mechanic whom had my business for years for this deceit, in charging for something that doesn’t take much effort-maybe mechanics need to learn more about customer retention then screwing someone just because so many fear the ominous check engine light. Checking the reason for a check engine light and the code is about as difficult as checking the oil level. There are too many mechanics that take advantage of customers. I appreciate the honest ones. And my word of mouth will go far in getting him more business.

  • Jason says:

    I own an auto repair shop. While what you mention can be true, you are not looking at the entire picture. NAPA, Advanced, etc.. will scan your car free of charge and give you a “LIST OF ITEMS THAT COULD CAUSE” that code. They did not diagnose, test & know with 100% confidence after installing this part your car WILL be fixed.

    We have over $25,000 in OE scan tools. What happens when it isn’t your gas cap? Is it unfair to say the shop you took your vehicle to deserves to spend 1 or 2 hours of work to figure out the problem, and do so free of charge; all while having to pay $25k in equipment to be able to diagnose & repair your vehicle?

    Most mechanics have $10k to $20k in tools IN EACH toolbox. Should our mechanics work for $10 dollars a hour and still have to pay huge amounts of their paycheck for regular tools to fix your car?

    This article has upset me. Most people doesn’t understand how expensive it is JUST TO HAVE THE TECHNOLOGY AND EQUIPMENT required to fix your car. I can’t even tell you how many times somebody has came from Advanced Auto, etc.. with new parts they want installed. After it is installed they have the same problem and they are upset. Advanced doesn’t diagnose. They SELL PARTS. A Code p0301 – cylinder #1 misfire read from a scanner isn’t proof you need a tune-up. A P0440 isn’t proof you need a gas cap. Putting a flow meter on the EVAP system and seeing a 0 leak IS PROOF. But with proof comes expenses.

  • Michael says:

    I have 2005 Dodge Neon SXT and I figured out how to reset the checking engine light after you have fixed the problem. You can not pull the neg battery post off and do,but if you pull the fuel pump fuse that is located under the hood it will reset it

  • Kim says:

    Have a 2005 Saturn L300. Check engine light on forever. Had the diagnostic thing done at auto zone. Mechanic fixed something. Still on. But there is not a clear list from the diagnostic test. A list of 6 items. Just a bunch. How do i know where to start? Is there a place where i can find out exactly what is wrong. At 2 separate occasions i would be driving for awhile. Then stop at s light of something and at the start again my car would “buck” when the car seemed to shift. Any ideas?

  • Brandon says:

    Ive been a tech for years… Im one of the “honest” ones… I don’t think anyone knows or understands how a lot of us flat rate techs get paid… Say a job comes in a truck needs cam phasers, a common repair on a 5.4L truck… The job pays 3.5 hours… If this job takes me 8 hours I get paid for 3.5 hours… A auto part store diag is a joke! The author dident take into account that auto part stores have these scan tools to sell auto parts.. So what they do is get the code type it into their computer and say “oh you need *this part*” ive seen it done.. I worked at a part store. Vehicles are getting more and more complicated every model year.. Say you spent 150 dollars on a fuel pump and had a buddy come over you paid for his time and you go to turn the key on your truck and it still doesent start… What then? Take it to the dealer and find out your relay failed.. a 6 dollar part. The diagnosis fee pays for my time and training, which, ive spent my entire career training and taking time away from my family. Don’t get me wrong there are shady mechanics… But this fee is what gets me through the bad weeks.. Especially in winter when things are slow. Not to mention that more often then not it takes longer to complete a pinpoint test then the charge is.. Id like to invite the author of this text to be a flat rate mechanic and talk bad about diag fees… I believe he’ll see things different.. Go get some wrenches get out from behind your desk and bust your knuckles then talk….

  • Matt says:

    Why is it that every person is a technician all of a sudden? If you were all so smart, you would understand that a check engine code is a starting point for diagnosis. While the code may state a failure with a part and that part may have failed, that is only a 50/50 and a total shot in the dark. We call those people parts swappers! Ask your doctor to try something he is not very sure of without diagnosing, its only your life he guessing at!

    Take Look at the car manufactures diagnostic trees for diagnosing trouble codes! Some of them are extremely elaborate and are time consuming. Yes, an evap emission leak may be a fuel cap as they definitely fail from constant use but again its 50/50 and certainly a cheap solution to start with. A check engine light does not always mean fuel cap or oxygen sensor as your local parts stores like to constantly recommend. Places like these give professional repair facilities a bad name and give this industry a black eye.

    I must say that this article is a bit insulting in the fact that I personally know how much time, sweat and blood some vehicles have caused. I have spent my whole life being a car doctor and while some issues are very simple a lot are not and please do not paint a picture to people that check engine lights are a dirty little secret because they just are not.

    A $2 pocket scanner is not a tool! Someone should really take a close look at the investment that a good technician makes in their life, its more than your cars worth I guarantee. They constantly have to buy new tools, diagnostic equipment and have consistent continuing education to learn new technology as it changes way too much! Good techs get beat up, cut and bruised constantly with no real thank you from anyone, just a crappy article like this from someone who knows nothing else besides what they do for a living. Sorry, venting!

    A customer that came in recently with a traction control light and a code that stated loss of communication with abs control module. If I followed the logic in this article I would have replaced the abs control module to the tune of $1200. Instead, we performed electrical diagnostics and followed a manufacturer diagnostic tree which was 8 pages long and took 1-1/2 hours to perform but the cause was the engines exhaust gas recirculation valve. Wow, this isn’t related to brakes or traction control at all. How could this be? the computer didn’t say the exhaust gas recirculation valve was bad? Total customer invoice was $550 with diagnostics, huh?

    I understand writing this is a total waste of time because most people have their mind made up because they believe what they hear or read but when you try to explain something you know more about, I hope your audience listenes to you!

    • Loretta Frecker says:

      Your post is on the spot thank you.

    • ronnie says:

      Thank you!! Haha. I see this all the time. And of mechanics used this way of thinking and just started swapping parts then customers would be pissed when it doesn’t fix it and you gotta do more. Ok you have a bad cat.. what made the cat go bad? You can put a new cat in and it’ll just go out again if you don’t diagnose the actual problem (assuming the cat didn’t just go bad)

  • Loretta Frecker says:

    Very miss leading article I work in a Auto Repair shop as the Office manager and I hear our service advisors daily explain that the code pulled at the local parts store is not a diagnostic it has become a big issues of honest shops because the code pulling makes us look like crooks.

    The practice of part stores pulling codes and selling a bunch of parts just to sale parts is such a disservice to the customer, this practice is about greed period.

    For the article to say the scan tool tells the technician exactly what part is wrong and this is our dirty little secret is ridiculous it just show that the writer is very uneducated in the area of auto repair. Come on people use your heads

    • ronnie says:

      Where I live in california it’s now illegal for parts stores to pull codes. So many times I have had customers say..well auto zone pulled the code and said it was this.. I did it and my light is still on

      Haha. a code isn’t a dam diagnosis! That’s like saying a bad cough is a doctors diagnosis. no.. it tells you where about the problem is and gives you an idea.

  • flash girl games says:

    Fine way of explaining, and good piece of writing to obtain facts on the topic of my presentation subject, which i am going
    to deliver in university.

  • John says:

    As a professional technician myself, I can’t help but to laugh at some of these replies. Proper professional auto repair and servicing costs money, period. I’ve made a significant investment of time and money(lots of money) to be the best I can be in my work. Ive always tried to be as fair and forthcoming with my customers as possible. People need to realize that cars are extremely complicated machines. Most cars have multiple computer controllers that run an array of different systems on their vehicles. The check engine light on your car is a generic indicator of a problem. A problem that might be a loose gas cap or or might be a failure of any number of electrical or mechanical components on the vehicle. Anybody with a 20$ code reader can pull a code from a vehicle. It takes a skilled professional to properly determine the cause. Not interested in fixing it properly? I have the cure for your check engine light problem. Grab some electrical tape and cover the light on your dash and hope for the best.

    • ronnie says:

      Haha yes! People are so ignorant. They think mechanics have a magic machine that tells exactly what’s wrong with your car in 5 mins. They aren’t charged to read a code..they are charged to diagnose the problem right which takes good time and knowledge and really expensive tools. People come in all the time to my work and get mad we charge 89$ to diagnose the problem.. then they do it themselves and come back and fail smog. Haha

  • ronnie says:

    Getting a dam code out of the car isn’t DIAGNOSING. shops charge to diagnose the problem properly . Not just read the code. The code gives you an idea of what and where the problem is. tell me what you do when you get the code… small evap leak. And when it’s not your dam gas cap. It takes time and diagnosis. People always get mad and think mechanics have a special magic machiene that they hook up and it tells you everything that’s exactly wro g with your car. Haha. Not true. Even if you get an oxygen sensor code.. most of the time it prob is the oxygen sensor but also a lot of the time it’s not.. what’s making the o2 sensor go bad? I see all the time people fixing their car cause they have a code reader and it doesn’t fix it!

  • Triple D Tech says:

    So what if a mechanic charges that much, its not about the price its about getting the car fixed.Imagine going to the Auto parts and have the plug up the machine they will tell you the code but will not be diagnose there more likely have you buy the part install it and boom there goes $75 gone to waste, but wait you can’t return electrical parts that been installed so they got you there. If you ask me its better to pay what its worth instead of installing parts after parts and get no results

  • Judy says:

    I have a code 107 what does that code mean to help me figure out on my car 2000 Malubu

  • Judy says:

    I have a code 107 what does that code mean to help me figure out on my car 2000 Malubu , engine light is on

  • Shane says:

    Will a obd2 scanner tell me what cods have been erased (ie by used car salesman to hide a problem) thank you

  • Chris says:


  • paul brotherton says:

    yeah right….. the humps at the parts store dont know anything. It takes a qualified technician with lots of training to diagnose a check engine light. Stop trying to buck the system morons. Those charges cover the costs of training and pay for the technicians time to go over your car and do a lot more than just ‘read codes’. The mentality of anyone rolling up to a building that some person had invested hundreds of thousands of dollars into to make money and expecting a freebie is just stupid.

  • abc says:

    It’s time to file class action lawsuit against these incompetent govt. clowns. Do you realize that the car repair industry was directly involved in creating this obdii smog system and now you have to pay $hundreds of extra repair dollars to the car repair industry. They should only be allowed to require that your vehicle does not smog. Now they require that your vehicle does not smog AND you have to pay for the complicated computer smog crap they put on your car. There used to just be expensive, complicated test equipment at the smog station. Now they’ve put complicated, expensive test equipment on all of the millions of cars- that you have to pay to maintain. It’s fraud and incompetence.

  • Lynne says:

    I have a 2002 Chrysler Sebring . Just had over a thousand dollar worth of work done on front end, plus new tires . . Now the check engine light is on & diagnostic check shows “no code” . . Does this mean that the computer is shot or is there other ways of checking & resetting . . Or worse case senario . . how much does a computer cost ?? I’m sure more than I can afford at this point . . sigh !! Thanks for comments . . .

  • mike blackwell says:

    I have a 94 town car I bought at a yardsale for 500 dollars in 2009. Previous owner had put in a rebuilt 97 4.6 towncar motor in 2005 due to 94 4.6 had upper engine defects (valve stem seals cheaply made started leaking oil ) that caused other issues to develop. I think the shop just put all the external parts from the 94 on the 97. The IAC, egr and ports got carbonized from prior 94s oil leaks into cylinders. This caused transmission to fail from improper shifting times because the pcm was trying to adjust engine operation with the improper air flow from the egr and iac not working right. I had transmission rebuilt, 3, 000 dollars. Didnt know why trans had failed at the time. Check engine light would come on when going over 40 to 50 mph, go off at slower speeds. Transmission shop could not figure it out reading the eec and pcm codes. They put in two different computers, still had check engine light problem. They gave up. Three years later, wife had been driving in city only, I used Seafoam to clean intake manifold (injected into throttle control body over 15 minutes) and the check engine light finally went out. Still had one issue, engine would not have any power if cold. Had to warm up to operating temp and it was fine. No check engine light showed up. My wife was not happy having to prewarm engine before she could drive it. It would bog down, if you pumped gas pedal it might move the car, it usually died tfying to drive it cold. It would idle fine cold, just would not drive at all. I finally decided a happy wife equals a happy life, so I determined myself to fix this issue. I did not take it to a mechanic or dealer. Instead I spent about 20 or more hours scouring the internet, forums, googled all I could think of and educated myself. I have always been fairly mechanically inclined, electronics, radio repair in 10 years military. 10 years civilian life as electrician apprentice and 20 years maintenance and Hvac repair after that. Retired now but still like to keep my hands busy. So I decided, after searching the web, that the iac was bad. 42 dollars from advance auto, a bear of a time swapping it out from between the firewall and back of engine and under wiper motor assembly(thin long fingers helped) and I was done. I thought! I pulled battery wires off for 30 minutes and put back to force the pcm to relearn idle and such. I cleaned the maf sensor, throttle body, replaced pcv valve and a few suspect vacumn hoses. I started the car and it actually drove right off while cold. Power was excellent, decelerating was handled by the iac perfectly. Then the idle speed all of a sudden went up to about 3, 000 rpms. It would not come down. Turned motor off, disconnected battery overnight and started car again the next morning after reconnecting the battery and the rpms were still way too high. Put it in gear, car jerked forward due to transmission getting hit with 3, 000 rpms from a dead stop. Decided to put back in park and turn off engine and rethink the whole situation. A day and 15 hours on the internet later and I bought a 47 dollar tps (throttle position sensor, attaches to shaft on right side air intake valve on throttle body) from Napa auto parts and swapped it out with the old one, the screws were threadlocked in the aluminum throttle body. I had a heck of a time getting those out. Penetrating oil, small gas torch, twelve inch diagonal cutting pliers and a prayer were all it took.HaHa. The tps had stuck open setting the rpms so high. It was hard finding that info, only one minor mention of that happening to a tps on the internet after 15 hours reading. Lots of mentions of intermittent contacting of signal due to worn tps resistive traces inside of the sensor, but only one mention of sticking high. Thanks for taking the time to read this. I hope my story might help someone else. I learned that not all engine troubles cause a check engine light to come on, also that just city driving adds to carbon build up, needs to be run out on the highway also, this helps to keep carbon from building up so bad.also learned putting off fixing a small problem can turn into bigger and worse problems. Also, disregard the check engine light at your expense. It is note to just to make money for the dealer. Sometimes it can be your savior, or your cars’. Thanks again.

  • J.J says:

    If you want to buy a “car computer scanner”, search online for OBD Scan Tool (OBD II is for 1996 and newer cars and OBD I for 1995 and older). I’m a DIYer and own several car diagnostic tools, and have learned that these car scan tools will rarely give you a “a-ha!” spot-on diagnosis. For the most part, it’ll give you some direction but you’ll still have to get under the hood to test suspect sensors, wires, or car parts (mostly electrical parts) that are likely tied to that check engine light. If you don’t know how to work around a car’s electrical system, get a Power Probe 3 and google online troubleshooting tutorials for your car (example: 2004 Nissan Sentra 1.8 fuel injector testing).

    • J.J says:

      Another thing. Those guys at the auto parts stores can’t help you with your check engine light. It’s no more than an auto parts sales business. You’ll very likely end up buying parts that won’t fix your problem. With some guidance, patience and provided that the problem isn’t too complicated, you could fix your problem. Some people get impatient and frustrated and start buying parts that they “think” will fix the problem. Bad strategy. Stay far away from that. However, if you’re stumped after testing suspect wires or components, then you’re going to have to pay for a tech’s expertise.

  • Mechanic says:

    So for all you mechanic bashers who think your local mechanic should work for FREE, How do you expect your local mechanic to pay for that needed $3500 to $6000 scanner that does a lot more than your $15-$65 piece of crap scanner that may or may not get you in the ball park. Or how do you expect your local mechanic to pay for his/her training on how to use said scanner, You know the training that they take time away from their families by going to classes held after work at night so they know how to properly diagnose your vehicle so that the guess work is not done resulting in wasting your hard earned money ??????? Pay the $75-$95 diagnostic fee and quit your griping, You will by far waste more money than that guessing here and there.

  • Coach says:

    While at the auto parts store also get your battery and alternator checked for free.
    Often a weak cell in the battery (even one that will still crank the car) will cause false engine codes. A good diagnostics is the biggest part of repairing a car cheaply, so you only repair the real problem and don’t do a lot of unnecessary repairs. Mechanics charge for it because it takes their time away from paying jobs and many people will take the free diagnoses and try to fix it themselves. Not a problem for the auto parts store who may sell parts, but it is a problem for a mechanic who gets nothing for it. Many shops will apply the cost of the diag. to the cost of the repair if you get it fixed by them. Dealerships are the most expensive place to take your car and I never take mine there unless it is warranty or recall work. Some diag. codes tell you exactly what is wrong and it is an easy fix, but some will just point you in the direction and there is actually mechanic work to find the problem. That takes time and knowledge and costs money. Some problems especially electrical, computer and misfire problems require expensive diagnostics equipment to figure out and to fix. Too many mechanics read the codes and replace parts without confirming the problem. That often leads to an unresolved problem that has to be repaired again for an additional cost. They never say “my bad” no charge. It is kinda like going to the doctor, they charge you if they are right or wrong fixing your problem. A good mechanic is like a good doctor and is worth the cost when he diagnoses your problem correctly and fixes it the first time. You may drive your car with the change oil light on (but please change the oil) but never continue to drive with your mil, cil, engine light on. It is most times a serious problem and if it begins blinking that means raw fuel is entering your catalytic converter which will destroy the cat and you will still have the original problem to fix that is causing the raw unburnt fuel in your exhaust. Many times the light will not come on until it is stored twice.

    • Coach says:

      Forgot to say, if your battery and/or alternator is bad replace them first then clear diagnostic trouble codes or ask auto parts store to clear them. Many times the weak or incorrect electrical supply causes all sorts of trouble codes to be set. Todays cars are sensitive regarding electricity. I had an Acura dealership advise me to get $2,500 of repairs done due to engine codes set on my Acura, then they said, ‘Oh by the way your battery has a bad cell and you need a new battery also” I had them put a new battery in and clear the codes and drove for years without another problem. BTW I fix almost everything on my cars myself and have a lot of tools and knowledge to do so, but I take it to a mechanic technician for diagnoses and difficult repairs. I pay him for his diagnoses and it is worth the cost.

  • Coach says:

    Buying a used car and don’t know a lot about cars? I hope you know a good mechanic. Always, always, always have a used car checked out by a good mechanic. It will be the best money you ever spend. Make sure you test drive the car a couple of times. When you test drive it stop somewhere and turn the key off so you restart the car, because some codes don’t turn on the engine light until the second time the car is driven. Tell the seller you are taking it to a mechanic to get it checked out. If they resist, walk away no matter how good you think the deal is. The mechanic should drive the car, again allowing it to set codes and should check for obd codes with his computer/code reader. The codes will show up even if the light is disabled. I think I know a lot about cars, but I still get a mechanic check before buying a used car especially if sold “as is” and most used cars are sold “as is”. Don’t buy a house without getting it inspected. Don’t have major surgery without a second opinion. Don’t buy a used car without a mechanic inspecting it. The last used car I bought was inspected by my mechanic, then I took it to a transmission specialist for a second inspection of the transmission, then I bought the car. If you don’t have or know a mechanic, shop for one before you shop for the car. Tell them you are shopping for a car and want them to inspect it. Make an appointment with the mechanic for the inspection. Be prepared to pay for the inspection and agree on the cost before hand. If you use the mechanic for repairs they may not charge you or they may.

  • Coach says:

    Repair Manual. If you are going to work on your own cars, buy the repair manual for it. It is worth the money in saved time a and information it provides. A lot of diy selfers will try to figure it out as they go. Save yourself hours of pain and problems by having the repair manual for your car. It contains detailed instructions in most cases and photos to show you where things are and how they go together. Take pictures as you take things apart to help remember how they go back together and take them from more than one angle. That is about it for my advise, good luck to you!

  • William Cantrell says:

    I am an automotive technician of 35 years. The manager where I work sometimes dosen’t even pay me for diagnosis or half pay. The problem isn’t the mechanics it’s corporate America taking all the gains and desiding when to or not to pay. Sometimes the diagnostics take hours. Sometimes minutes. For us we never get paid more than an hour. We’re lucky when someone hasn’t tried to repair it before we get involved. Don’t get me wrong there are incompetent technicians and honest managers and owners. They are the ones that give our industry a bad name.

  • Scott says:

    This article does nothing to help people with fixing their car.
    I’m an ASE Master Tech with L1 Advanced Engine Diagnostic certification. I fix problems other shops run away from.

    If you come to my shop with a check engine light AND NO OTHER SYMPTOM, we read the codes for you for free. If the code points to a quick and easy problem such as a loose fuel cap or other easily checked item, we don’t charge to check the issue.

    However, I’d say about 3/4 of the cars that come in with check engine lights on have a more complicated issue that requires more testing. By a guy like me who actually knows how vehicles work.

    The reason many parts stores quit reading codes and/or interpreting them is they were being sued for selling parts that didn’t fix the problem, because parts stores don’t have the capability of actually diagnosing the problem. Unfortunately there are many mechanics who should be parts-guys too, because they do the same thing.

    Here is a good tip for everyone. If you have a check engine light on, take it to a shop with certified mechanics. Ask for a preliminary code scan (hopefully that’s free). Then if they want to sell diagnostic time, ASK THEM IF THEY HAVE A LAB SCOPE or other diagnostic equipment aside from their scan tool. If they don’t, they aren’t truly capable of diagnosing your car. They are getting as far as that scan tool can take them and then guessing the rest of the way.

    Paying 100 dollars to get answers about your car sucks, but it’s far better than paying more for someone to guess.

    If you thought you were having a heart problem, would you go to the doctor and pay tests to find out, or go to Walgreens and use their free blood pressure machine?

  • Valerie says:

    Had a problem with the EVAP high purge flow had it fixed took it to have it inspected a week later and he said it was not ready it had 5 codes that needed to be cleared. He told me that we had to drive it to get the codes to clear. Took it back in today to have another inspection done and he said there are two more codes that needs to be cleared. He told me that we had to let the car sit for 24 hours without driving or starting it does this sound correct

  • Bri says:

    IMO it’s worth buying the scanner. Every car after 96 has the ability to be scanned by a code reader. Now the $100 scanners will read and delete most codes but not all. I had an airbag code that needed to be reset by the readers that are in the $1000 range, thankfully a friend has one of those and was able to reset my airbag light. My scanner has been very helpful to me, my wife, my brother, my parents, and friends cars. Yes they only point you in the direction to check so you should know where to go from there. If you have no mechanical skills you’ll still be in the mercy of the garage you go to for the repair. But having the scanner saved many trips to the garage for things that were simple fixes. Yes I threw codes for gas cap issues but also for other more complicated repairs like misfires. My mothers colbalt just had a dead battery from leaving the lights on, after we jumped it the car had check engine light on and the dash display read “service traction” which was not displayed before the dead battery. Apparently the jump start threw a glitch in the computer and when I scanned it, it came back with 36 error codes lol. Needless to say, I erased them and its been fine ever since and I’ve scanned it twice since then with no codes returned. So yes it’s worth buying the cheap scanner if you plan to own cars the rest of your life.


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