"Check Engine" Light Came On. What Could It Be?

Discussion in 'General Motoring' started by Pamela G., Dec 19, 2006.

  1. Pamela G.

    Pamela G. Guest

    Hi, I have an old 1991 Hyundai Excel. The engine light came on during
    the last 1/2 mile on my way home last night. What engine parts could be
    screwed up? Would the light be telling me I have a problem with low oil
    or low water or would that have it's own designated light icon?
    Pamela G., Dec 19, 2006
  2. Could be a lot of things. Did you just get gas? If so, the gas cap may be
    loose and that can give a signal. If that is the culprit, it will take
    about 15 or 20 starts to go away after tightening the cap.

    Oxygen sensors go bad also. Very common cause. To know for sure, you have
    to use a computer for readout of hte information. The car is still drivable
    as is, but there may be long term effects if you don't get it check out soon
    to know for sure what the problem is.
    Edwin Pawlowski, Dec 19, 2006
  3. Pamela G.

    Guncho Guest

    This happens to me all the time after getting gas if I don't tighten
    the cap enough.

    ('99 Accent GSI)

    Goes off after a few days fo driving after tightening the cap.

    Guncho, Dec 19, 2006
  4. Pamela G.

    hyundaitech Guest

    Pamela's car is pre-OBD-II, so the fuel cap idea is out.

    The computer has no way of monitoring the oil level, so that's out, too.

    It's possible the coolant is low and you set a code for the coolant
    temperature sensor because the temperature got too hot.

    Realistically, I'd need to know the trouble code to give you a good idea
    of why the lamp may be on. What it means is that the computer has
    detected a problem with the fuel management system.

    If you've got an analog voltmeter, you can try to read the trouble codes
    yourself. Go to www.hmaservice.com (requires Internet Explorer) and
    register for a free account. In the shop manual for the 1991 Excel, there
    will be an explanation of how to read the codes with a voltmeter.

    If you're unable to read the codes yourself, you should take it to a shop
    capable of reading the trouble codes. The dealer will be able to do this.
    If you're considering taking the car anywhere else, call first to see
    whether they can read the trouble codes on the car. Since it doesn't use
    OBD-II diagnostics, many shops won't have the tooling required to do this
    type of diagnosis.
    hyundaitech, Dec 19, 2006
  5. Pamela G.

    Pamela G. Guest

    Thank you all so much for the info! I didn't drive it all day yesterday
    after seeing the "Check Engine" light come on the previous evening, but
    today I started it up and to my shock the "Check Engine" light didn't
    come on!!

    I don't know why it didn't come back on but it sure is alright with me!!
    And it never came back on the whole afternoon I was driving it. I
    suppose it will appear in time so I'm going to find a mechanic with the
    computer stuff that can diagnose it

    Hyundaitech, thank you for the details on how to get the codes (I'm
    going to save that for future refference), but I wouldn't know the
    difference between a voltmeter and a muffler bearing!! Ha!! I just
    recently finally found the transmission dip stick!! That little sucker
    sure is hidden! Really, it's almost _under_ the engine!

    Would you happen to know how long it should take a mechanic to actually
    run that test on my car? I mean, could I drive it in and within an hour
    have the results, or would I have to leave it all day for them to keep?
    Reason being, I wonder if I'd need to rent a car for this situation.
    Pamela G., Dec 21, 2006
  6. When I had an oxygen sensor go bad, the light came on, went off, came back
    again, off again, then finally stayed on. Since car don't repair themselves
    it is a matter of time for it to come back.

    As for how long it takes to get the codes, if the mechanic can do it right
    away, it is only minutes. The problem is, most will not just drop
    everything to pull your car in to check it on the spot, but will want you to
    eave it for some time. Once the problem is determined, it could be minutes
    or hours to get the part and replace it. That, of course, varies at each
    Edwin Pawlowski, Dec 21, 2006
  7. Pamela G.

    Guncho Guest


    If your "Check Engine" light is not on, the mechanic will not be able
    to read the error code, as there isn't one.

    Guncho, Dec 21, 2006
  8. Edwin Pawlowski, Dec 21, 2006
  9. Pamela G.

    Guncho Guest

    Guncho, Dec 21, 2006
  10. I probably wouldn't either for a one time deal. There are times that the
    light will go on and the "problem" is corrected by a fresh tank of gas or
    some outside source like that. OTOH, engines don't repair themselves so if
    it does come on repeatedly, it will eventually need fixing.
    Edwin Pawlowski, Dec 21, 2006
  11. Pamela G.

    hyundaitech Guest

    Again because of your car's age, the check engine lamp works a little
    differently than it does on most of the newer cars we discuss here. In
    many cases, if the problem isn't present when you start the car, the lamp
    will stay off until the problem reoccurs. The trouble code should remain
    in memory for something like 50 key cycles, though.

    A good shop (with the required tools) should be able to have the trouble
    code for you within several minutes. The problem is that it may require
    significant investigation to determine why that code set. You're best off
    to plan on all day and be pleasantly surprised if it's quick than to try it
    the other way around.
    hyundaitech, Dec 21, 2006
  12. Pamela G.

    Matt Whiting Guest

    That is your choice, but keep in mind that some failures can cause
    expensive damage, in particular damage to the catcon. If you'd rather
    spend $800 to replace the catcon than $60 to find out which sensor is
    getting flakey, that is your choice.

    Matt Whiting, Dec 21, 2006
  13. Pamela G.

    Guncho Guest

    I guess I'm hesitant to shell out the cash for a check engine light
    that has gone off on it's own accord considering that this happens to
    me at least once every few months if I don't crank the gas cap after
    filling up.

    Older cars are different so maybe it's worth it.

    Guncho, Dec 21, 2006
  14. Pamela G.

    Matt Whiting Guest

    I've never had the gas cap set off my MIL light, but then I don't find
    correctly installing the gas cap to be that hard. :)

    If you are sure that something like that is the cause, then I agree it
    is wasteful to spend the $60. However, if something else is wrong and
    you are dumping too much fuel into the engine, you can easily toast the
    catcon and that is a very expensive repair generally.

    Matt Whiting, Dec 21, 2006
  15. Pamela G.

    Guncho Guest

    I know you don't believe me but if I don't turn the cap til I hear like
    12 clicks, the light will come on. Is the problem my gas cap? Would a
    new gas cap solve the problem?

    Guncho, Dec 21, 2006
  16. Pamela G.

    Matt Whiting Guest

    Yes, I would think something is defective with your gas cap. I turn
    mine until it clicks and then stop. I probably get 2-4 clicks just from
    inertia, but I don't attempt to turn it beyond the first click that I
    hear. If the cap isn't cross-threaded, it shouldn't take more than a
    one click to seal as the torque should not increase behind the first click.

    Matt Whiting, Dec 21, 2006
  17. You pump your own gas? Sorry to hear that. In NY and parts of MA it is
    forbidden to pump your own. Funny thing is, the full service is cheaper
    than most self serves. This (pump yourself and save) is the biggest scam
    ever foisted on the driving public.

    Self serve in my town in CT is 2.579, but I bought full service in MA today
    for 2.329. It is probably even cheaper in NJ. Last time I was there I paid
    1.939. I'll be damned if I'm going to freeze my ass off and pay more for
    the privilege.
    Edwin Pawlowski, Dec 22, 2006
  18. Pamela G.

    hyundaitech Guest

    The reason gas is cheaper in NY and NJ has much more to do with the state
    gasoline tax than who is pumping. I'd be interested in seeing a
    cost-comparison chart by state if we normalized the data to remove taxes.
    Unfortunately, I'm not up for spending the time to put it together.
    hyundaitech, Dec 22, 2006
  19. Pamela G.

    Matt Whiting Guest

    Actually, I prefer to pump my own gas just as I prefer to change my own
    oil. That way I know that the gas cap was replaced correctly and the
    drain plug for the oil likewise.

    It isn't forbidden to pump your own gas in NY. I live in PA and work in
    Corning, NY and they have lots of self-serve stations, actually I only
    know of one or two that still pump gas for you. Maybe you are thinking
    of NYC.

    Full-serve, where available around here, costs 2-5 cents per gallon more
    than self-serve. Why do you think it is a scam? Do you think the
    person pumping the gas is working for free?

    That certainly isn't the case around here. I don't mind pumping my own
    even at below zero temps. Maybe you should move south where it is
    warmer. :)

    Matt Whiting, Dec 22, 2006
  20. In MA, each town fire marshall determines if the motoring public can safely
    pump their own gas. In the towns that are full service, the price is the
    same, sometimes a penny or so cheaper, than the self serve. They still
    manage to pay that (usually a high school kid) pump jockey a wage and make a
    profit. In my CT town, the self serve is competitive, but if you want full
    service, they charge you 20ยข a gallon more for the kid to come out and pump
    for you. They are really saying they don't want to do it. That is a scam
    if the guy up the street can pump it for the same price. We were told by
    the big oil companies that they were offering self service as a cost benefit
    to the buyer. The fact is, they kept the self service price the same and
    artificially raised the full service price well beyond what it should be. ,

    No reason to move; too many bugs in the south. I just have to be thoughtful
    as to where I buy my gas. In 45 years of driving, only once was the cap not
    tightened properly. The town where my office is has self service, but the
    next town over where the warehouse is, has full service at the same price or
    a penny less. So, I just buy my gas the next town over when I go there.
    Keeps those kids out of trouble and they can earn some beer money.
    Edwin Pawlowski, Dec 22, 2006
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