CEL and bad smell from exhaust with codes
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Cadillac Seville / Cadillac Eldorado Forum Discussion, CEL and bad smell from exhaust with codes in Past Cadillac Vehicle Discussion; ...
  1. #1
    bwv565 is offline Cadillac Owners Enthusiast
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    CEL and bad smell from exhaust with codes

    The Check Engine Light is illuminated (solid yellow/amber) and I have the following codes:

    PCM P0420 Current Catalyst System Efficiency Below Threshold (Bank 1)
    DDM U1713 History Loss of Front Door Module to Window Motor High Speed Comm.
    IPC U1016 History (cannot find the description for that one)
    IRC U1016 History Lost Communications With XXX
    TTM U1016 History Loss of communication to PCM


    There is a terrible smell from the rear of the car after turning the engine off, I can't tell if it's fuel or if it's the typical "rotten egg" smell from catalytic converter problems but actually i feel nauseous from just smelling it for about 3 seconds.


    From what I've read about the P0420, it seems as though it's catalytic converter time. Recently I also had the Check Fuel Gage message but filling the tank and replacing the gas cap seemed to fix that, and the message has not reappeared.

    Ugh.
    Catalyst System Efficiency Below Threshold (Bank 1)

    Read more at: http://www.obd-codes.com/p0420
    Copyright © OBD-Codes.com
    atalyst System Efficiency Below Threshold (Bank 1)

    Read more at: http://www.obd-codes.com/p0420
    Copyright © OBD-Codes.com

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    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: CEL and bad smell from exhaust with codes

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  4. #3
    Mafiaman111 is offline Cadillac Owners Fanatic
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    Re: CEL and bad smell from exhaust with codes

    With a p0420 that means converter is bad and with that smell you describe its toast, and I have never heard a check engine light turning red

  5. #4
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Check engine lights don't turn red. Blinking indicates a misfire (don't drive the car in that case).

    And in general:

    Amber dash lights - Have the vehicle serviced when convenient (CEL, ABS, TCS...$.

    Red dash lights - Pull over as soon as possible or damage and/or injury may occur (Oil pressure, engine temp, brake fluid...).

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    bwv565 is offline Cadillac Owners Enthusiast
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    Re: CEL and bad smell from exhaust with codes

    Quote Originally Posted by MoistCabbage View Post
    Check engine lights don't turn red. Blinking indicates a misfire (don't drive the car in that case).

    And in general:

    Amber dash lights - Have the vehicle serviced when convenient (CEL, ABS, TCS...$.

    Red dash lights - Pull over as soon as possible or damage and/or injury may occur (Oil pressure, engine temp, brake fluid...).
    MC do you have an approximate idea of what kind of $$ I'd be looking at if the catalytic converter (not just the o2 sensor) has to be replaced?

    Yes the CEL is amber and solid. But the smell from the exhaust is so noxious that seriously no exaggeration I felt nauseous about 5 minutes after getting into my house.

  7. #6
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Depends on the brand. ~$75-several hundred dollars.

    These cars tend to throw catalyst inefficiency codes if a cheap converter is used. Stick with a well known brand.

    Rotten egg smell? Have you checked your FPR?

  8. #7
    bwv565 is offline Cadillac Owners Enthusiast
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    Re: CEL and bad smell from exhaust with codes

    Quote Originally Posted by MoistCabbage View Post
    Depends on the brand. ~$75-several hundred dollars.

    These cars tend to throw catalyst inefficiency codes if a cheap converter is used. Stick with a well known brand.

    Rotten egg smell? Have you checked your FPR?
    No, I'm not sure if it's a rotten egg smell or fuel. Actually my grandfather had a boat many years ago, that had a very distinctive odor from the exhaust and what I'm smelling on the STS is almost identical. I know catalytic converters have the rotten egg smell when they're bad, I also remember that from my mom's 70s Ford and Dodge cars.

    Re: FPR, no I have only so far checked/pulled the current and history codes, and know the symptoms (smells).

    Remember also that I had the Check Fuel Gage issue? That hasn't come back but I think you may also be on to something there.

    Damn I wish things would stop breaking on this car.

    Interesting that one of the codes was also related to window switch (DDM U1713). I've also reported in these forums about the windows going up and down full auto but do not stop mid way. I don't think that's something I'm going to fix, same with some of the buttons on the steering wheel for audio controls not being backlit any longer (nuisance but tolerable).

    One other thing I notice, is that the car has a rough idle at cold starts, for about 15-20 seconds then the RPMs drop and it's as smooth as can be, to the point sometimes of my wondering if the engine is actually still on.

    Thanks for help.

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