What Your Check Engine Light Is Telling You

Edmunds.comEdmunds.com Member, Administrator, Moderator Posts: 10,237
edited June 2017 in Editorial
What Your Check Engine Light Is Telling You


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  • go32233223go32233223 Member Posts: 0
    How to remove a 02 sensor that is too tight to move with a 10 inch extension on the socket,,go32233223
  • sparky70sparky70 Member Posts: 1
    I have a dodge caravan with 280, 000 miles on it. I drive it everyday. I burn BP or Shell gas. I change the oil religiously. The timing chain/ water pump has been changed. It has new spark plug wires, but I need new plugs. Once in awhile the check engine light comes on. The light usually comes on when I am sitting not moving with the engine on. I turn the engine off restart the engine and this shuts off the light. I have to change the plugs soon. The car is just rusting out badily. If you have a Dodge Caravan, keep driving it until you see the road through the floor board....peace........................g.smith
  • lehrer1lehrer1 Member Posts: 54
    Very good article.
  • donnie15donnie15 Member Posts: 1
  • roadguyroadguy Member Posts: 1
    3 points to comment on.
    1 Fine Tuning 2] Oil change & 3] Check Engine/Service lights AKA"idiot lights"

    I own a '97 Chevy Tahoe which sports a 350. I get exceptional mileage and performance without any extra bolt-on or expensive gadgets.
    I bought the "Hoe" 5 years ago from an old gentleman that used it on his farm. Not the prettiest thing in the world, but it does suit me well for work and travel.
    When I bought it, it had been somewhat abused, so I set out to "un-abuse" it...

    1] Fine Tuning: A mechanic friend who happened to be a Chevy guy told me that the manufacturer sets the engines [computer] to meet the minimum EPA standards.
    He hooked up his laptop, pulled up all the info and "dialed in" EVERYTHING.
    My Hoe went from a engine shuttering POS to a Silky Smooth tune.
    BTW when he had it hooked up, the 'Puter told him I was getting 8city and 12hwy.
    When done, It said I would get 17C and 21H.
    On my road trips, I get an astounding 27highway...and I have a lead foot.

    2] Oil Change: Though ANY oil will be blackish after 50 miles, I test the oil "old school". I feel it and "light it up".
    Feeling the oil, you'll feel grittiness... or not. "Lighting it up" is putting a lighter to the oil on the dipstick...if it crackles...it has water in it. Change the oil.
    My MINIMUM is 5000 before change, but my standard is roughly 8000/10000.
    3] Service Lights: PAY ATTENTION to them. DO NOT ignore them. They're there to protect your vehicle.
    The "cheapest" way to find out what it is...MOST Auto Parts stores will check them for you...for free.
    Though some code readers are different than others, go to 2 places and have them plug in.
    99% of the issues are easily fixed...even if you're not mechanically inclined.
    I did recently get a code, had it checked, bought the part [$75.00], R&R'd the piece in 15 nimutes.

    IF a Light Does Come On...FIRST thing to do is REMOVE THE GAS CAP and Put it back on. Also, when you have the gas cap off, check it for broken/cracked seal.
    I've had friends that have spent upwards of $1000.00 with NO Improvement...only for me checking out their gas cap to find it in bad repair. $10.00 later...problem fixed.

    Happy Motoring Y'all
  • rickw123rickw123 Member Posts: 1
    If you have a check-engine light on, before running any diagnostics, first fill your tank with ETHANOL-FREE gas. (A lot of the older cars don't like the new 10% ethanol blend). If within 100 miles on the new gas, the light doesn't go out on it's own, reset it by disconnecting the negative battery cable and then reconnecting. You might have to go online to find a station that has ethanol-free gas in your area. Good luck!
  • rosieogrady1rosieogrady1 Member Posts: 1
    its also a good idea to get a second opinion when your dealer runs diagnostics and informs you you need 2 sensors and a complete exhaust manifold assembly for almost $1500. Took the car to an approved AAA station. They checked also - one sensor was shorting out the electrical system - why all kinds of lights came on. Wound up paying $449 for new sensor and car is running fine.
  • gunnthorgunnthor Member Posts: 1
    On my Mazda 3 diesel 2006 I've got fault code on the steering system C1278 ! Do I have to change some sensor ?
  • steverstever Guest Posts: 52,454
    A fault code helps you narrow down what system is having a problem. May not be a sensor problem at all. We didn't get that diesel flavor here in the US, but someone may know more about the code anyway.
  • fnlvnchkfnlvnchk Member Posts: 1
    Mine was a faulty gas cap. Cheap fix! I understand it is one of the main reasons the check engine light goes on.
  • barrywillsebarrywillse Member Posts: 1
    based on description of check engine light, I bought a veepeak wifi obd ii code reader from amazon.com and clear the trouble code. but if the trouble persist, the check engine light will come back, all of the code reader can not clear the trouble code.
  • southavensouthaven Member Posts: 2
    had air cond repaired last week, now have a "check Engine" light on my 93 Lexus sc400 car have first gen. OBD and just can't get the jumper wires pluged in to the test port. I think something got unplugged during the repair. Any Idea what the problem might be?
  • southavensouthaven Member Posts: 2
    Thanks but this car is OBDi. Can't use Code Reader, you have to use jumper wires at the test port, then read the number times the check engine light flashes. this give you the trouble code number. I'm just not able to get the jumper wire into the test ports. Going to Lexus dealer Tuesday
  • thecardoc3thecardoc3 Member Posts: 5,535
    Your Lexus does support scan tool diagnostics, it's just not OBDII. Most of the time it also takes specific pinpoint testing to prove why the computer is failing a given circuit or system.

    Articles like the one above were very poor representations of the work that technicians had to do in order to analyze and solve vehicle problems. What was even worse was that they were little more than advertisements for companies like CarMD and in this case AAMCO. Both of which were marketing their causes at the expense of people who were working very hard to try and keep up with the changes in vehicle technology.

    Click on the link for CarMD and it takes you to a website that sells their wares. They still try to promote the idea that all you have to do is pull the codes and that tells you what parts need to be replaced. It's taken a long time but if you read the responses in the forums today you can clearly see that most of the regulars have learned that approach is the wrong one and now they are starting to take a better approach. The trouble code when generated by the computer does NOT tell you what is wrong, it tells you what test failed. Now you need to find out what that test was, how the computer runs it, and then you have to test the circuit or system the same way that the computer does. AAMCO and other companies who pushed "Free Diagnostics" route forced their techs to be less disciplined in their approaches and that is coming back to haunt them.

    Today there is a shortage of qualified technicians. It takes twenty years to really master the trade but that comes with the caveat that there is no finish line when it comes to having learn more. Meanwhile there are still way to many entry and early career techs that don't earn the kind of living that will see them stay in the trade long enough to learn to be really good at it. Articles like the one above did more to discourage people from pursuing a career as a technician than it ever did to help someone fix their car.
  • hamburger2hamburger2 Member Posts: 1
    The CHECK ENGINE light in my 2006 Chrysler PT cruiser [only 62K miles] is always on. I have been told that it's OK as long as the light does not blink. However, I can't get through inspection without spending $1,200 - only to find that after driving about 100 miles the light comes back on. This happens EVERY year for as long as I had the car – bought as a demo car from Reedman in Langhorne, PA! I am afraid that I might have a problem with the light itself and the shop is happy to keep charging me these horrendous amounts to get me through inspection, and then have the problem again next year! Should not the CHECK ENGINE light identify WHAT needs to be fixed?
  • ray80ray80 Member Posts: 1,655
    Check engine light can be for numerous problems and code needs to be read to find out where/what to look at. If you are getting the SAME thing fixed over and over to get through inspect, it might be time to find a better shop.
  • isellhondasisellhondas Issaquah WashingtonMember Posts: 20,338
    The Check Engine light has been called "The 500.00 light" and for good reason!

    Ask me how I know....
  • chevrolet16chevrolet16 Member Posts: 1
    I have bought a obdii scanner from Foseal on amazon. it works fine with my Chevrolet truck, I use Dash Command as my reader, payed $9.99 for the app, worth it. I also use this OBD 2 while driving to provide data, hp, mpg, timing, etc...
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