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Thread: How to handle a "check engine" light

  1. #1
    Vulture of The Western World Eric's Avatar
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    How to handle a "check engine" light

    If the "check engine" (or "service engine soon") light comes on, your car's computer (On board Diagnostics, or OBD) is probably trying to alert you to a problem or fault, typically with the emissions control system. It's not immediately urgent - you can continue to drive the car - but you should get it looked at (or check it yourself) as soon as possible because at the least, your car is not running as efficiently as it should be (which means it's probably getting less than optimum gas mileage). If you drive long-term without getting whatever's not right fixed, you may cause damage to costly parts such as the catalytic converter.

    The nice thing about the "check engine" light and OBD is that the car actually tells you what's wrong with it.

    The not so nice thing is it's telling you in code. And you'll need an OBD code reader to access (and decipher) those codes.

    Scanners are available from about $50 on the low end for a very basic model to as much as $300 or so for a professional model. The lowest cost models often only reveal the alpha-numeric code but don't translate what the code means. You need to possess (or buy) a book that lists the possible codes - and their meaning - for your particular vehicle. You're probably better off buying a model that not only reads the codes, but also tells you what the codes mean.

    Using the gauge is very simple. All cars from model year 1996 and up have a standardized plug-in port (very much like the hook-ups you'll find on the back of many desktop computers) that's located in the area under the steering wheel/dashboard on the driver's side of the vehicle. It will be immediately obvious once you get down there to look for it. The gauge will work on any 1996-up OBD car or truck, irrespective of make/model.

    The scanner will come with directions, but in general, you simply plug the unit's connector into the OBD port, turn the ignition switch to "run" and let the reader do its thing. It will communicate with the car's OBD computer and in a moment, whatever code triggered the "check engine" light to illuminate should be displayed. You can now fix whatever the problem was - or at least know what the problem actually is before you take the car in to be fixed by someone else. This can help protect you from being ripped-off by an unscrupulous or incompetent shop.

    The scan tool will also let you turn off the "check engine" light by "clearing" the stored codes after the problem is fixed (or before). But keep in mind that unless you actually fix the problem, the system will just turn the "check engine" light back on a few miles down the road.

  2. #2
    Senior Member DonTom's Avatar
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    "You need to possess (or buy) a book that lists the possible codes - and their meaning - for your particular vehicle."

    Or just do an internet search on the code. For an example, on my trip to Canada, the biggest problem I had was my check engine light came on with a code P0171.

    I did a search on "P0171" and got this.

    -Don- SSF, CA

  3. #3
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by DonTom View Post
    "You need to possess (or buy) a book that lists the possible codes - and their meaning - for your particular vehicle."

    Or just do an internet search on the code. For an example, on my trip to Canada, the biggest problem I had was my check engine light came on with a code P0171.

    I did a search on "P0171" and got this.

    -Don- SSF, CA
    Good info, Don - thanks!

    PS: How about contributing an article (or two!) here...?

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    A lot of the auto parts stores around here will read the codes for free.

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    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by dBrong View Post
    A lot of the auto parts stores around here will read the codes for free.
    Yes, here (SW Va) also. Advance Auto does it.

    Still, it's nice to have one of these OBD readers in the tool box. I'm having lots of fun with mine!

  6. #6
    Senior Member DonTom's Avatar
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    Quote Originally Posted by Eric View Post
    Good info, Don - thanks!

    PS: How about contributing an article (or two!) here...?
    It cannot be this week. Tomorrow, I am going on my yearly backpacking trip. The weather, even at 7,000 feet elevation, looks good for the entire week. I just hope nothing changes from the weather reports I see now on the web.

    I will be off line for the next week (and impossible to get a hold of).

    -Don- SSF, CA

  7. #7
    Senior Member DonTom's Avatar
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    Quote Originally Posted by Eric View Post
    Yes, here (SW Va) also. Advance Auto does it.

    Still, it's nice to have one of these OBD readers in the tool box. I'm having lots of fun with mine!
    It seems you're getting over your severe case of technophobia.

    -Don- SSF, CA

  8. #8
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    Quote Originally Posted by DonTom View Post
    It seems you're getting over your severe case of technophobia.

    Beat me to it!

    How long before he buys a cellphone?

  9. #9
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by DonTom View Post
    It seems you're getting over your severe case of technophobia.

    -Don- SSF, CA
    Somewhat.

    I still luvs carbs, though!

  10. #10
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by Dave Brand View Post
    Beat me to it!

    How long before he buys a cellphone?
    Never!

  11. #11
    Senior Member eesquared's Avatar
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    PepBoys and AutoZone will read them for free here.....but only if you have an OBD 2 or 3 car! They do not have the OBD 1, which is what the Elky needs. I had to order one, and I am still waiting on it to arrive.

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    I thought OBD1 cars would flash a light and buzz a solenoid to give you a code when you shorted a particular pair of pins in the connector.
    Only tool needed is a paper clip.

  13. #13
    Senior Member grouch's Avatar
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    Quote Originally Posted by MikeHalloran View Post
    I thought OBD1 cars would flash a light and buzz a solenoid to give you a code when you shorted a particular pair of pins in the connector.
    Only tool needed is a paper clip.


    OBD I systems were sometimes a real paint to extract codes from. Ford and Toyota you had to short out pins and then count the sweeps on an analog volt meter or blinks on a reader. GM is a little easier, you use a little tool to short two electrodes in a connection under the dash. Mopar is the easiest as you don't start the engine but turn the ignition on, off, on,off and then on and leave it on. It still blinks out a code but you don't have to jump through hoops. Even after they went to OBD II, you can still pull codes by doing it. The reader is easier and you can erase them too.

    All in all, I prefer the OBD II system. It's been tweaked through the years and is a good tool to find trouble spots in engines.

    By the way, I'm not aware of an OBD III system but I don't fool with cars until they are several years old. (Most of my stuff is from before the turn of the century.)
    Honk if you love Jesus.

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  14. #14
    Senior Member eesquared's Avatar
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    I was looking at Sears for the OBD 1, and the only one they had that would read the OBD 1 was a $200 multi-OBD that read OBD 1, 2, and 3.

    I don't know what the 3 is either, but that's what the label said.<shrug>

  15. #15
    I prefer none! Give me an engine with mechanical systems and I'm good to go, all these sensors in modern cars piss me off.

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