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Home » Auto Ownership

The Service Engine Light: Your Mechanics Dirty Little Secret

Last updated by on 107 Comments

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 $19. And there’s a bluetooth-enabled OBD-II scanner for just $23. 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 & 7,500+ others by getting FREE email updates. You'll also find every post by category & every post 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

        • 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.

        • 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.

      • 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.

    • david says:

      gas cap leaking… Yeah RIGHT

    • 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.

  • 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!!!!!!

  • 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…

  • 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.

  • 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

  • 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

  • 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:

    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

  • 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.


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