Help Ecm/PCM Questions
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HT4100 4.1, 4.5, 4.9 Discussion, Help Ecm/PCM Questions in Cadillac Engine Technical Discussion; I have a 92 Seville With a 4.9 Im getting Loss of PCM Data Were is the power train control ...
  1. #1
    frizz3333 is offline Cadillac Owners Member
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    Help Ecm/PCM Questions

    I have a 92 Seville With a 4.9 Im getting Loss of PCM Data Were is the power train control module and is that the same thing as the body module and the ECM if not were all those located the car runs great then all at once the service engine soon light will come on and it acts sluggish and missfires i lose the fuel avrage gauge and the speedo flat lines. I plug the OBD tester in the plug under the seat and turn the key in the one position and it says it cant comunicate with my ecm but when i push the warm and off button i get code IO39 and Code I034. And would the computer work then not work then work again. If someone could tell me tje location of these componets that would be great I dont think its a ground problem but im check to make sure the starter to body ground is nice and clean to see if that helps the problem.

    IO39 Loss of RoadSending suspension Data

    IO34 Loss of Power Train Control Module

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  3. #2
    frizz3333 is offline Cadillac Owners Member
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    Re: Help Ecm/PCM Questions

    Well i loosened the ECM under the glove box and i can cause the problem to start and stop by tapping the ecm box with a wrench So i think i found the problem symptoms were Was Code I034 Service engine light would come on transmision would feel week and the car would run rough. The speedo and fuel avrage would flat line.

  4. #3
    ewill3rd is offline Cadillac Technician
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    Re: Help Ecm/PCM Questions

    Definitely possible. On those cars the communication systems were very hard to diagnose.
    Due to the design of the data bus it can be a real trick to figure out which module is actually causing the issue. It sounds like you might be on to something, and thank God if that is it. I won't even tell you horror stories about working on cars of that time frame with communication issues.
    It can be bad.

  5. #4
    frizz3333 is offline Cadillac Owners Member
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    Re: Help Ecm/PCM Questions

    Im usually Pretty good with auto eclictrical diagnostics and i noticed alot of people have the same symptoms i had but never really got a clear answer only bad thing now is if i get a computer off ebay or somthing i hope that takes care of the problem does anyone know if I have to take the chip out of my Ecm and put it in the new one or do i just plug the knew one in and the car will learn and reprogram new computer it self?

  6. #5
    ewill3rd is offline Cadillac Technician
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    Re: Help Ecm/PCM Questions

    You need to swap your PROM into the new computer.

  7. #6
    frizz3333 is offline Cadillac Owners Member
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    Re: Help Ecm/PCM Questions

    Thanks thats kinda what i thought what exactly is the purpose of that is it somthing with the security system or does each Cadillac run diffrently from the next?

  8. #7
    ewill3rd is offline Cadillac Technician
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    Re: Help Ecm/PCM Questions

    The calibrations in the PROM are based on things like final drive ratio, tire size, emissions equipment and what have you (as an example)
    There are several different PROM IDs for each production year based on options.
    The one you get could be the same, but it may well be different. Best to swap the PROM out to be sure the base cals are right for your specific vehicle.

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