Bought a OBD II Code Reader for Check Engine Light

Several months ago my “check engine” light went on. I went to my local mechanic, who plugged in a code scanner and found my error. Since it didn’t re-appear after resetting, he said he could try to fix it ($$$) or I could just leave it and it might never come back on. He said he normally charges $50 just do do the diagnostic, but this time it’d be free. A week ago, it came back on, and of course I wasn’t eager to go through all this hassle again.

I decided to try and buy my own error code scanner. If you search for “OBDII”, “OBD II”, or “OBD 2″ code readers, these devices will plug into your 1996 or newer model year car and read the diagnostic code from your car computer. In addition, they can erase or reset the code so that you can see if it is an ongoing problem.

Luckily, while searching I ran across a post on Fatwallet that had this CodeKey OBD II code reader on clearance for $23.90. There are nicer scanners out there, but they usually start at $60+. From the CodeKey site:


Simply put, CodeKey™ is an easy to use device designed to unlock the mystery of why your vehicle’s Check Engine Light is on. The Check Engine Light can ignite for something as simple as a loose gas cap, or as serious as a fuel leak. A flashing Check Engine Light can be serious, and continued driving can cause permanent damage to the vehicle. Until now, you would need to rely on a mechanic to determine what problem caused the light to go on

When you know the source of the problem you can:
* Decide if you should go to the garage immediately.
* Determine if the problem is something you can fix yourself.
* Know what to expect when you bring your car to a garage.

Other options
If you go to a dealership and have them read this code, it’ll cost you $100 just for the “diagnostic check”. Some people report that your local Autozone may lend these out for free at the store. I have also read that some Jiffy Lubes let you use theirs if you pay for some service like a oil change. I’d call first.

The old-school method is to simply disconnect your car battery and wait for the computer to reset itself. But for cars newer than 1996, this site reports that wiping out the computer’s memory can affect the operation of the transmission, climate control system and other functions. You can also trigger your alarm system or anti-theft car radio into lock-down mode. However, you won’t know the actual cause of the problem.

In the end, at less than $25 I just bought the tool. Just avoiding the gas to/from the mechanic and having to arrange a carpool for pickup/dropoff would be worth it. And sure enough, after resetting the light it has not come back on again.

It turns out, buying this tool could be the start of a new side business. Check out this Craiglist ad where a guy will come over and reset your light for $25. Learn how to do common repairs, and there you go. I think I’ll pass, but don’t forget to deduct business mileage if you go this route! ;)

Comments

  1. “Autozone may” is misleading. Pretty much ever AutoZone and Advance Auto Parts I’ve been to offers free CEL reading. I’ve used the service more than once, and seen it being used many other times.

    The closest Autozone comes to talking about it that I can find is here:

    http://www.autozone.com/in_our_stores/free_testing.htm

  2. That is a great price for an OBDII scanner. I bought mine for $100 a couple years ago, I think it has more features but I never use them. Might want to point your readers to a site like http://www.obd-codes.com/trouble_codes/ that will interpret what the codes mean.

  3. I had a need for one a couple of years ago and Auto Zone helped with it. They didn’t just lend it to me, they came outside and did the whole reading for free.

    I will say that this diagnostic is not the same as the more detailed ones that some shops perform. This can sometimes give a generic message that could apply to several different things. For instance, mine gave a message that could have applied to either a spark plug misfiring, the coil malfunctioning, or one other issue… a trip to the shop narrowed it down to the spark plug misfiring.

  4. more than likely, you left your gas cap loose, causing vacuum leak, triggering check engine light. tighten the cap and reset the light. done.

  5. Just went to Schucks this past Saturday to use theirs. So far my CEL hasn’t come back on. Its likely some bum part on Fords that is none to go bad. I’m just hoping it was the cold weather giving it an issue.

  6. That’s pretty cheap. This would make a good backup scanner to keep in the trunk. Thanks.

    Unfortunately AutoZone stopped lending these out in California about a year ago. I was told that the new policy is tied to a new/amended emissions law- I guess some desperate people were clearing all codes before going in for a smog check. I tried asking at several locations and got the same reply.

  7. Maybe it was specific to my car, but I was able to read the code and reset the light on my 98 Sentra with a simple screwdriver.

  8. What was the code?

  9. cheap man’s way is to put a paper clip between the 1st and last plug and read the blinking light. They will give out a code. and look up the code on the web.

  10. Be careful. Last time I checked there were two types of ODB II code readers. I’m guessing the latest ones are compatible with both types. Cars after 1996 use OBD II and some cars after 2004 use ODB II “Can-Bus”. I of course bought one in 2004 and it wasn’t compatible with my 2004 F-150. Thankfully my F150 has never had the check engine light come on. I use it on my other cars and friends cars.

    These things are great and I’ve used them for years. Even if your not a DIY type when it comes to cars, it’s worth the cost just to see the mechanics face when you walk into a shop and tell them your car is “throwing a P010 code”.

    I started out using a metal key (or a wire) that would ground out the input on pre-1996 cars and you had to count how many times the check engine light flashed to get your code. LOL.

  11. Your link brought me to parts america at $50 plus shipping. Am I doing something wrong? Thanks

  12. If your mechanic could have charged you $50 he would have.Find a new mechanic who won’t make you you feel like he is doing you a big favor every time you have a simple question.

  13. I usually just go to Autozone because the check it for free.

  14. good topic.

    If you have a VW, it is better to get a VAG-COM. This is a VW specific tool so you can get a lot more information and also make changes.

    I know people who use the autozone free check. That’s a good option, but If you have the scanner you can do troubleshooting over a period of time in cases where you have intermittent issues.

  15. Tom Woolf says:

    That OBD II reader was $24 in only certain areas. $50 for the rest of us. But if my engine light was on now, I’d go buy that for $50 vs. giving it to my mechanic (nothing against the mechanic, really).

  16. well, that may be the case, but are you going to pass that emmision test? I doubt it! Next time when you take your car to do emmisions, their equipment will indicate no information-so they cannot let you go. Either way bad investment for removing the light or buying the instrument! Be advised!

  17. I got an OBD because my car’s emissions light came on when the gas cap was not tight. The dealer said it would take 20 cycles for the light to go off. What a pain. I think, I paid $50 for my OBD.

  18. srodgers71 says:

    Love the Blog, Jonathan- and as it happens… I’m an ASE certified Master Technician. I think it was very sharp of you to get your own Code Reader. I would only caution that sometimes a service code- won’t necessarily tell you whats wrong with your vehicle- e.g., O/2 sensor code sets when a vehicle has a vacuum leak, so the unexperienced guy buys/installs an O/2 sensor- when the real problem was the vacuum leak. Don’t “jump” to conclusions when retrieving a service code. Use sites like the previous Poster mentioned: http://www.obd-codes.com/trouble_codes/ to do a thorough diagnosis. At the very minimum though- a Code Reader will get you going in the right direction, and could point to an easy fix- like a loose Gas Cap… and its definetly worth the investment just for that. If you have questions regarding the code that you retrieved- Drop me an email- I may be able to offer some helpful advice.
    srodgers71@hotmail.com

  19. Thanks for the recommendation. I was looking for one a few weeks ago. Instead I took it to my mechanic and similar to your experience, my mechanic told me that it will be free this time but he will start charging me in the future.

  20. Where do you plug in the device?

  21. Advanced auto will let you use the one they have for FREE. I was lucky and found out that I had a small emissions leak. If I would have gone elsewhere they charge 100 dollars just to run the test.

  22. I have had mine come on twice and it was always the gas cap loose….. If it comes on a little after filling your gas tank then…. :-)

  23. Susie, there is a socket close to the handle that opens the hood. You can reach it with your left hand when sitting in the driver’s seat. It’s at about driver’s lap level under the dashboard.
    Jonathan, I’m sure that guy from craigslist doesn’t report that $25 so there are no miles to deduct. If he paid taxes on that he’d be broke, wouldn’t even be worth the driving.

  24. I bought a cheap one of these a couple months ago as well. The Autozones in my area do free checks at their stores but I was going frequently enough that I though this might be worth it. I also thought it would be nice in case the light went on when I wasn’t close to any Autozone.

    It should be noted though that these things are not just for resetting the CEL light. Check the code first to make sure the issue is not serious. The book that came with mine gives some idea of the severity of the code. If it is a serious issue, you probably still want to take it to a mechanic. Most of the issues with my car though I have been able to take care of myself.

  25. If you want to reset your check engine light, pull the battery for a short while…

  26. As Jonathan mentioned, “The old-school method is to simply disconnect your car battery and wait for the computer to reset itself.”
    If there is nothing actually wrong, that will work but on modern vehicles that may really create problems as Jonathan mentioned.

    Using a scanner will reset the light but if there is an actual issue the light will reappear because there is something wrong (hence setting the DTC). Also, as someone else mentioned it is quite common for “generic codes” that could be a number of different items & will require actual mechanical knowledge to diagnose.

    $50 for a diagnostic is a great price, I would not expect a mechanic to do it for free as Tom suggested above. I am not a mechanic but I feel as a trade that have a bad name because of some of them are bad apples. A code reader could save you many trips to a real mechanic but if there is something wrong this will not solve it for you. My $.02.

  27. Now when you say that you cleared it did you right down the code? There is usually a larger issue present if it has come back multiple times. Here is a link to a website that lists the p-codes and their meanings. http://www.obd-codes.com/trouble_codes/. If it comes back match it to the code in the list and then go talk to a mechanic.
    I would really hate for you to be stranded somewhere with an issue that could have been resolved long before.

  28. I can also attest that Autozone in California will not lend out the scanners anymore, but for different reasons than listed above. The Autozone guys said it was because the dealers and auto mechanics lobbied the State legislature because it was taking away a profitable business for them, and the argument was that Autozone (and other car parts stores) were not qualified to diagnose the codes and therefore sold consumers parts they didn’t need. My car-guy neighbor said that codes are stored during an accident and people clear the codes to avoid liability, or people clear the codes to make it easier to sell salvaged cars.

  29. Stealerships. they’ve written themselves into the laws pretty well over the years. It may be why they still exist even though people often take a big disliking to them. I’d prefer to buy my car directly from the manufacturer… but this is against the law also!

    I suppose it is true that simply looking at a code does not directly tell you the correct part. however, sometimes it does. I think you could replace 2 or 3 wrong parts (until you find the right one) at your own cost and still have this be cheaper than paying the dealer to possibly get the correct part. I would say don’t get me started… but I already have!

  30. Mark,

    It may be cheaper or it may cost you more as parts relating to a CEL are rarely that cheap. A competent shop will get it right the first time & prides themselves at not taking the “we’ll see what works” approach & charging for all of it.

    There are probably more bad shops than good, hence the reputation but when you do find a good one, you’ll know. Ironically, I just had a CEL come on in my car & I do have multiple scanners but my car is a 1997 Honda that is covered by a 14 year/150,000 emissions warranty. I took the gamble that the CEL was likely an emissions issue (which 90% of the time it is) so I didn’t look at the code at all.

    Just got the call that it was a misfiring code that even the Dealer couldn’t figure-out what happened to set the CEL but looked at everything thoroughly to make sure there wasn’t an active issue. I took a gamble & lost but even if I pulled it myself, I would have had to go to a shop anyway to discover the source of the misfiring so it would have cost me the same & now I have the time back that I would have spent screwing around with it & getting nowhere.

  31. I use a ScanGauge. It’s more expensive (~170, IIRC), but in addition to scanning/resetting codes, it can pull all sorts of cool sensor data, calculates mileage/fuel remaining/lots of other stuff, and just generally makes me smile every time I get in my car :)

  32. wow, great advice. I didn’t know they were that cheap, I thought they were $100-200.

  33. rubin pham says:

    also it does not take much to learn how to change the oil in your car.
    just read the car manual. you can save a few hundreds dollars a year this way.

  34. Okay, it seems like none of the point that you *MAY* be costing yourself more money in the long run.
    Though OBD II is a standard, each manufacturer implements it in different ways. many DTC’s (diagnostic trouble codes) are of a ‘delay’ type. This means that your Check Engine Light will not come on until the ECU has detected a fault in, say, 7 of the last 10 operating cycles. A good example of this type of a code is a cylinder misfire code.

    If you clear this code every few weeks and keep driving, there is a good chance that whatever component is STARTING to go bad is going to go completely kaput, which can often take other components out with it. Another situation would be an O2 sensor that is starting to go, and simply resetting and ignoring the problem will put more wear and tear on your engine, AND will give you a significant drop in fuel economy.

    Just to note here, I am NOT nor have I ever been a mechanic, and I certainly don’t endorse the $100 charges to read a simple code. I do have a lot of experience as a ‘backyard mechanic’, but by day I am an accountant.

    This post really isn’t tinged with any personal interest on my part, but if you CEL is flashing, often your car is trying to tell you something. Sometimes it won’t be major and will go away on its own (gas cap open), but sometimes ignoring it will end up costing you far more in the end. Your best bet is to read the code, look it up on google. If you don’t understand what it means, take it to someone who does.

  35. I’ve had the engine light come on quite a few times on my Jeep. Per the manual, it says it’s not an urgent matter. After having it checked out the first time, they had to replace the gas cap as it had a leak. Since then, I’ve been able to just remove and reinstall the cap and the light goes off. Has to do with making sure there is a vacuum when the cap is on.

  36. great article. but I checked the link and it doesnt mention the cars for which the code reader will work. Any idea if they will work on a BMW?
    thanks!

  37. Piece of advice – AutoZone lets you use theirs for free and are pretty good at figuring out codes.

    My CEL (on a 2000 Toyota Corolla) kept going off and it ended up being a tempermental MAF sensor and it cost over $400 to diagnose and fix (replace). I had done research on my car’s problems associated with CEL going on and attempted to clean the MAF with contact cleaner, but the mechanic said it was gone a while before that….good luck!

  38. Update: I bought this scanner yesterday online and picked it up in store. It works but is R E A L L Y slow compared to the ones Autozone used to lend out in their California stores (and are now not allowed to by the State).

    I keep getting an intermittent P0401 code on my Toyota Camry that comes and goes for last 4 months. Could be my gas cap is lose, or any number of 4 expensive parts of my EGR system need to be replaced.

  39. Kevin,

    This is exactly why you’ll need to go to a professional anyway. Just don’t tell them what needs to be fixed! It’s rather offensive to the trade in general.

  40. Like Autozone, O’Reilly’s will also loan you a code reader for free, and it only takes a couple of minutes to read the codes. I looked up my code (P1441 Evap System Flow During Non-Purge) online and determined that it wasn’t critical and I could safely continue driving my car as needed until I had time to diagnose the problem. I read more about the evap system in my Chilton’s book and I may try to get it figured out this weekend. It should be a simple diagnosis and a simple fix. Until then, I’m driving my other car/toy, my old beater Bronco II (worth <$1k, but I love it). Instead of spending money on a code reader, I spent my $20 on a vacuum gage. Either way, diagnostic equipment will pay for itself many times over by keeping your car out of the shop and by preventing you from replacing the wrong parts.

    Also, Kevin, read this link for info on the P0401 code: http://www.obd-codes.com/p0401
    I don’t know a lot about EGR systems, but I don’t think the gas cap has anything to do with it. There are a couple of cheap things you can try before you start throwing expensive parts at it. That link has more details. Good luck!

  41. This is exactly why you’ll need to go to a professional anyway. Just don’t tell them what needs to be fixed! It’s rather offensive to the trade in general.

    I sure as hell do if I know what the problem is. I’ll discuss it enough to make sure they understand that I know what I’m talking about, and then just ask them to do what I want without wasting a bunch of time. Yes, there are a lot of customers who don’t know what they’re talking about, but there are a number of us who do.

    If you have some reasonable mechanical skills, the easiest way to figure out a lot of the problems is to read the engine code and google your car model and the code. For most common models there are several big car repair forums that you can find that will discuss the problem, fixes, and any issues with the fixes in detail including pictures. Just remember, “a man’s got to know his limitations.”

  42. To Dave,

    I researched this code extensively online months ago and you wouldn’t believe the number of complaints about mechanics who tell their customers they need to replace part after part until they finally replace the right one (with no refunds on the previous unnecessary part replacements), instead of spending the time to properly diagnose the problem which requires taking out each part and testing them independently. The point I am getting at is that it makes logical sense to take a complex problem to a professional, but you don’t always get what you pay for.

    I also found it interesting that a number of honest mechanics were posting on car enthusiast message boards asking the online community to help diagnose a car they were working on.

    To Nomad,

    The reason the loose gas cap can cause this code is because it is a pressurized system and any air leak (loose gas cap, hole in a hose) will prevent it from working. More than likely there is a carbon buildup over the years that is causing a valve to stick every so often. I probably need to change the diaphragm in the EGR valve or change the VSV solenoid (which is in an impossible place to get to), but I’m hoping that a simple cleaning will do the trick.

  43. ericblair,

    Well said. There is a wealth of information available to fix your own problems. There are only two things that make me take a problem to a professional – lack of time and/or a lack proper tools.

  44. I sure as hell do if I know what the problem is. I’ll discuss it enough to make sure they understand that I know what I’m talking about, and then just ask them to do what I want without wasting a bunch of time. Yes, there are a lot of customers who don’t know what they’re talking about, but there are a number of us who do.

    A shop that is willing to just go on what their customers tell them to replace is not one worth patronizing in my opinion. They should always do a proper diagnosis no matter what. It is in both of your best interests that this occurs in case you are potentially wrong. Then the shop looks bad & you’re angry.

    Having worked in a shop & knowing personally knowing mechanics (good ones), I know that it is a major pet peeve of theirs to be told what is wrong with their car & to do just exactly that whether that let you know that or not. This said, “knowing what you’re talking about” in general will prevent you from getting screwed although it’s been my experience that people who really do stay out of shops altogether unless they lack tools/space/health to work on their own cars.

  45. I researched this code extensively online months ago and you wouldn’t believe the number of complaints about mechanics who tell their customers they need to replace part after part until they finally replace the right one (with no refunds on the previous unnecessary part replacements), instead of spending the time to properly diagnose the problem which requires taking out each part and testing them independently. The point I am getting at is that it makes logical sense to take a complex problem to a professional, but you don’t always get what you pay for.

    I also found it interesting that a number of honest mechanics were posting on car enthusiast message boards asking the online community to help diagnose a car they were working on.

    Actually, I do believe it. As I mentioned above, I believe there are more bad mechanics than good that’s why it is important to establish a relationship with a good one that you can trust.

    Personal example, I have a Civic that I believed needed a brake job because it was impossible to me that brakes (even drum brakes) could last over 100K. A dishonest shop would have done the job & sent me on my way & I would have been happy. My mechanic refused to do it, even showing me a new shoe vs. old & how the wear was not significant.

    To reward his honesty (& not make the time-consuming trip to this great shop a waste) I let him pick something else that needed to be done (a muffler, which he previously told me was on its last legs).

    The point is there are a lot of sub-par shops & mechanics that don’t know what they are doing & as mentioned above replace parts (& hope for the best). I would never accept this & neither should anyone else, it’s time to move on to another shop.

  46. The code reader may read the code correctly but want be able to reset it.
    I bought an Actron reader for $100, even that cannot reset the code.Light keeps coming back.
    I was told at the dealer that newer obd computers need re flashing to reset.
    Mine is an I30.
    Just an fyi.

  47. Kevin,

    Again, I’m not familiar with the EGR system, but I do know a little about the Evap system since that’s where my problem was. A loose gas cap should throw a code for the Evap system, not the EGR system. It sounds like you have done your research though. Hopefully you are right and it is just a carbon buildup. Good luck getting it fixed :)

  48. The code reader may read the code correctly but want be able to reset it.
    I bought an Actron reader for $100, even that cannot reset the code.Light keeps coming back.
    I was told at the dealer that newer obd computers need re flashing to reset.
    Mine is an I30.
    Just an fyi.

    A $100 code reader is going to have many limitations since professional models cost several thousand dollars. It could just be that your car is not completely compatible with your scanner (i.e. need more sophisticated equipment, basically what the Dealer said).

    This is what I’ve been trying to get across in all of my posts. These “consumer” code readers are great for getting a rough idea for what is wrong but more times than not, you will need professional help to completely resolve the issue. Cars are not an investment, they are an expense & most people do not realize that the average car will costs hundreds every year to repair/maintain regardless of what you try to do yourself. Unless you have all the equipment & know-how, it will cost you. Even when you do, it will cost you (a mechanic friend of mine with a large fleet of vehicles was just bitching to me about tire costs because they are expensive even for the trade).

    It seems most everyone thinks that the only car costs are insurance, gas, & oil changes which is so far from the truth. I often see people give a car a bad review saying something like “tires only lasted 25K & brakes were warped @ 30K what a piece of crap!”. I just laugh about their unrealistic expectations of not spending any money on auto upkeep but I digress…

    I’m sure someone will tell me that they have 100K on original tires & brakes or something extraordinary like that & yes, that is remotely possible but not in the least bit likely. Cars are more expensive to drive than ever these days & it only seems like it is getting worse.

  49. My check engine came on a day before Jonathan’s post. Finally went to Autozone and got a free reading. P0141 sounds like I need to replace the O2 sensor. Easy to change myself, but its underneath the car.

  50. You have a net worth of 200k. You earn in six figures and now this. Man you are so Cheap. Enjoy life and live a little

  51. As an update, I live in Northern NJ and neither Autozone or Advance perform free diagnostic checks.

  52. Hey Car People,

    I just noticed in my recent copy of “Car & Driver” , April, 2010; they address this problem of interpreting the DTC Codes.

    If you have both an iPhone and a DTC code reader which gives you the OBD codes, there is now a free App. for your Apple iPhone. It will decifer the alpha-numeric code into Layman’s terminology. It’s contantly updated and will, at minimum, give you an answer you can read. (Possibly, less-likely to be a “Sitting Duck” in an unscrupulous mechanic’s shop. Again this App (an application you can download to your iPhone) is free.

    The name of this application is “FuzzyCodes”.
    Look for it along with the great “Car and Driver’s Buying Guide”. This App is, likewise, free.

    Good Luck!

  53. I have spent thousands of dollars and hundreds hours getting trained on check engine light/driveability why would I or any mechanic use our equipment or knowledge for free does the doctor do diagnostics for free ? If you want to replace parts to try to fix your car till its fixed be my and the parts store guest then when its still not fixed then come pay what I was going to charge you in the first place

    This is a simple code reader not a scanner my snap on scanner is 6500.00 and costs me 1000.00 a year to get required updates yes sometimes you can read a code and if it is a simple hard code you can replace a part and repair your vehicle and it is handy to clear/erase your code if you was working on your vehicle and left something unplugged yes you can buy this and save some money in some cases .You can also buy a hammer and nails and be a carpenter instead of calling a carpenter or you can get online and find medical tools ex. scalpel sutures etc. and be a doctor . Sometimes a part will fail and set a unrelated code some electrical parts are hundreds and thousands of dollars and I have seen time after time people change a 500 dollar part that wasn’t bad because a code was set and without pinning out a circuit replaced the part it didn’t fix the car and then they keep replaceing parts till they hit the jackpot or they say it cant be fixed if your check engine light is on there is other systems that shut down that could be saving you gas and believe it or not most repair shops do the same thing but they keep putting on parts until they hit the right part that fixes the vehicle. so yes this is a good tool I have a small code reader to read codes and clear codes when its too troublesome to do a complete setup with a scan tool..,….. but if your unsure seek a professional its not worth breaking down when you need to be somewhere or having a loved one break down late at nite or in a bad part of town……….

  54. Mike, please write in sentences with periods. Snap On tools are a rip off.

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