The Never-ending Check Engine Light
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Cadillac STS Forum - 2005 through 2012 Discussion, The Never-ending Check Engine Light in Past Cadillac Vehicle Discussion; Just after Christmas I bought a 2006 V8 (1SF) STS from a small town GM (not Cadillac) dealer about 90 ...
  1. #1
    dnett is offline Cadillac Owners Member
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    The Never-ending Check Engine Light

    Just after Christmas I bought a 2006 V8 (1SF) STS from a small town GM (not Cadillac) dealer about 90 miles from me. It only had 36K miles and is immaculate inside and out. When I test drove it, the CEL was on. Code is P2097 - Running rich post cat. The dealer changed the post cat O2 sensor and I bought the car the next day. When I got home, the CEL was on again. took it back and they reset the computer trims (I think). 3 weeks later, the CEL is on again - same code. Took it back and they replaced the pre cat O2 sensor. 1 week later, CEL on again. I then took it to a local Cadillac dealer. they talked to a GM engineer and did a static discharge on the electrical system. 2 days later. CEL on again. Back to the Cadillac dealer and they found the bolts on the air intake extremely loose and tightened them and cleaned the gummed up looking throttle body. 1 day later, CEL on again. So I'm going back to the dealer I bought it from - they won't pay someone else any more.

    Sorry to be so long winded...

    Anybody out there got any ideas??

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  3. #2
    carter's_sts is offline Cadillac Owners Connoisseur
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    Man, that's annoying. From what I've read from others on here, I'm surprised one of those things they tried hasn't fixed it, except for the alleged static discharge

    Keep us posted.

  4. #3
    1BadCadSTS's Avatar
    1BadCadSTS is offline Cadillac Owners Connoisseur
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    Sounds like me and my cam sensors lol

  5. #4
    dnett is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    Here's the latest update.

    Caddy dealer has had the car for almost 2 weeks. I'm picking it back up today. They have been on the phone with GM engineers trying to diagnose problem. They seem convinced that the problem is a vacuum leak somewhere or a small leak somewhere within the exhaust line. Tightened a loose clamp on a vacuum line on the brake booster. Supposedly pumped smoke thru as much of the vacuum lines as they could, but found nothing else. They kept it this long so that they could drive it some every day to see if the CEL came back on.

    Once again, I'm not too optimistic that this will fix the problem, but what else can I do....

  6. #5
    carter's_sts is offline Cadillac Owners Connoisseur
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    Black tape? Just kidding. I hope they got it fixed for you.

  7. #6
    dnett is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    Well, didn't even make it home before the light came back on again. The saga continues....

  8. #7
    Batarang23 is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    Frustrating...I hope they get it sorted for you quickly.

  9. #8
    carter's_sts is offline Cadillac Owners Connoisseur
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    Re: The Never-ending Check Engine Light

    The dealer didn't notice that after 2 weeks? I would try a different one.

    Quote Originally Posted by dnett View Post
    Well, didn't even make it home before the light came back on again. The saga continues....

  10. #9
    jdelp is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    I was having a CEL issue on my '05 also. I tightened the intake bolts - no luck, took it Cadillac dealer and had both cats replaced under manufacturer 200K warranty (don't recall details & which models/years it covers but you can find it on here) - again, no luck. Finally I found a thread on here about cleaning the MAF - so I bought some MAF cleaner at parts store, cleaned it & throttle body and have had no CEL for two + weeks now. Not sure if this would help, but for $7.99 can of MAF cleaner I'd give it a try.

    Good Luck!

  11. #10
    dnett is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    About 2 visits ago, they cleaned the throttle body - not sure if they did the MAF at the same time. If I had owned the car since new I would be tempted to just say the hell with it and drive it with the light on. But, since I just bought it and the problem was there when I bought it, I damned well want it fixed.

    I told the general mgr from where I bought it from that I wanted my money back and he could have the car - he pretty much just laughed in my face. Not sure what I can do, but I'm looking into it.

  12. #11
    malatu's Avatar
    malatu is online now Cadillac Owners Connoisseur
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    Re: The Never-ending Check Engine Light

    In Delaware, you can't pass an inspection with an Check Engine Light on.

  13. #12
    C&C's Avatar
    C&C
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    Re: The Never-ending Check Engine Light

    Same code (or different); inquiring minds (okay, maybe just me), want to know.

  14. #13
    dnett is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    It's been the same code every time - P2097 Rich Trim Post Cat. Where I live in Va, you can pass state inspection with the CEL on. There are some parts of Va where that is not true, though.

  15. #14
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    C&C
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    Re: The Never-ending Check Engine Light

    Wouldn't think it a vacuum leak, would want to run lean; your problem is rich. I'm not a tech (so my info is just thinking out loud). Goggle search yielded this: P2097

    Post catalyst fuel trim system too rich bank. Probable cause 1. Rich Air/Fuel ratio - Leaking injectors, regulator, high fuel pressure. 2. Incomplete combustion - Ignition or mechanical condition. 3. Failed H02S (Heated oxygen sensor)

  16. #15
    dnett is offline Cadillac Owners Member
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    Re: The Never-ending Check Engine Light

    The latest update.

    Took it back to the Caddy dealer 2 weeks ago. It had thrown some new codes: P0171 - lean fuel mixture and P0430 - bad catalytic converter as well as the P2097 code. They replaced the cat which was still under 8-80 warranty and replaced the gaskets on the intake manifold. Got it back after a week and on the second start, CEL on again. Had the codes read myself, P0171 and P2097. Took it right back and they decided to replace the ECM - also still under 8-80 warranty. Got it back last night and made it home, with a fill-up stop, and no light came on.

    We'll see...

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