This one even has me stumped
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Cadillac Seville / Cadillac Eldorado Forum Discussion, This one even has me stumped in Past Cadillac Vehicle Discussion; On the 97 ETC Ive replaced the cat as well as the front O2 Sensor But it keeps throwing bad ...
  1. #1
    CadillacSTS42005's Avatar
    CadillacSTS42005 is offline Banned
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    This one even has me stumped

    On the 97 ETC
    Ive replaced the cat as well as the front O2 Sensor
    But it keeps throwing bad O2 sensor codes on ALL FOUR O2 sensors
    Ive also noticed the car struggling to start (a weak start)
    Doesnt matter hot or cold.
    I was thinking FPR however, its weak to start even when cold....

    Any ideas guys?

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  3. #2
    Krashed989's Avatar
    Krashed989 is offline Cadillac Owners Connoisseur
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    Re: This one even has me stumped

    I'm thinking a circuit may be fried in the PCM... Time to call AJ.
    However, O2 sensors are not in use at start up so it may not explain that completely, unless the fuel injector drivers are affected by it or something.

    Before I jump to that conclusion though, what codes are being thrown?

  4. #3
    Raze's Avatar
    Raze is offline Cadillac Owners Enthusiast
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    Re: This one even has me stumped

    Jay,

    Get a multimeter on those O2 wires (harness side) and check for continuity w/the ignition switch set to on, but the car not running. I'm going to guess the connector or wire is bad, happens alot and can give erroneous failures to the PCM, happenend on my suspension harness...

  5. #4
    CadillacSTS42005's Avatar
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    Re: This one even has me stumped

    they dont all read bad at the same time though
    sometimes one will come up bad
    another time another will be bad
    sometimes all four

    and like i said its also the weak start, it has a new battery and new alt, im thinking starter and the weak crank (sometimes it starts and then dies, crank again shell fire) is causing the O2s to get a faulty reading...

  6. #5
    Krashed989's Avatar
    Krashed989 is offline Cadillac Owners Connoisseur
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    Re: This one even has me stumped

    Ahh... probably not the pcm then. How old are your spark plugs?

  7. #6
    Talamant3z's Avatar
    Talamant3z is offline Cadillac Owners Enthusiast
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    Re: This one even has me stumped

    hey is the o2 sensor before the cat easy to install?

  8. #7
    CadillacSTS42005's Avatar
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    Re: This one even has me stumped

    meh
    easy if you can get it on a nice lift

    and plugs and wires were replaced at 100k
    its got 115k now

  9. #8
    chazglenn3's Avatar
    chazglenn3 is offline Cadillac Owners Connoisseur
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    Re: This one even has me stumped

    I had the same problem on the '96 STS I used to own. Would get the O2 sensors to throw a code one at a time...all four of them. Traced it down to a common ground wire at the rear of the engine (firewall side). I think it was GND 300 or something similar. The four sensors all are ground to a lug there. Mine was broken off the block. Hope your issue is as simple!

  10. #9
    CadillacSTS42005's Avatar
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    Re: This one even has me stumped

    well i went ahead and installed a 3 inch high flow cat
    so far nothing has come back yet
    now i just need to trace down the weak start

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