94 sts strange issue

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Northstar Engines and System Technical Discussion Discussion, 94 sts strange issue in Cadillac Engine Discussion; I have a 94 STS that I really love. The problem is electronic with the computer interface and I think ...
  1. #1
    steelman is offline Cadillac Owners Member
    Join Date
    Jun 2003
    Social Circle, GA

    Unhappy 94 sts strange issue

    I have a 94 STS that I really love. The problem is electronic with the computer interface and I think that someone on this forum may be able to solve my problem. I transplanted a used engine into my 1994 pristine STS. I have had the computer replaced and speed sensor etc. and still have problems. When I disconnect the battery to kill the codes, then connect it again, I can start it and drive away with no problems. EVERYTHING WORKS WELL.!!
    I then turn off the key and restart and I get error message== Traction Control, ABS etc.
    No SIR codes, no ACP codes, The speedo doesn't work and I get TO73 and SO44.
    I have taken it to the dealer in Monroe, GA and they have no idea-- It must be the engine or something. Too old! Excuse me! The thing runs great when the codes are clear.
    I would also like to install performane enhancements.
    I love the car. Can someone help.

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  3. #2
    med's Avatar
    med is offline Cadillac Owners Member
    Automobile(s): 1994 STS "CADDYSNACK"
    Join Date
    Mar 2007

    Re: 94 sts strange issue

    I love this car too! The 1994 FSM pages 8c1-45,5e2-119 and 3g2a-43 indicate poor communication with PCM for all your affected systems. I don't know why reconnecting battery resets everything. Two of your codes share a common specific problem - "PROM in PDM no properly seated". I believe you need to use your old PROM (although I'm not sure) in your new PCM. Either way maybe the PROM is the problem due to either poorly connected in PCM or not the correct PROM. Hope this helps-let us know.

  4. #3
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Fort Lauderdale, Florida

    Re: 94 sts strange issue

    You said you replaced the computer AKA the PCM. The new one
    doesn't come with a prom/chip, you use the original.
    Sounds to me like is wasn't installed properly, I believe if
    you drop the PCM down and remove and reinstall the prom
    that will solve your problem.

  5. #4
    steelman is offline Cadillac Owners Member
    Join Date
    Jun 2003
    Social Circle, GA
    Thread Starter

    Re: 94 sts strange issue

    I'll try it.

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