PCM is staying awake causing 4.5 amp draw
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Electrical Technical Information Discussion, PCM is staying awake causing 4.5 amp draw in Item Specific Cadillac Discussion; I could use a little guidance as I chase this down: Here are the facts: PCM stays awake after car ...
  1. #1
    Avaya is offline Cadillac Owners Fanatic
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    PCM is staying awake causing 4.5 amp draw

    I could use a little guidance as I chase this down:

    Here are the facts:
    PCM stays awake after car shut down causing a 4.5 amp parasitic draw
    The PCM itself has been replaced and same symptoms
    I have pulled every fuse and relay and can see all the modules the PCM is keeping awake
    If I pull the PCM BATT fuse under the hood, the draw goes down to about .15 amp

    So now I need to find what is keeping the PCM on (without a Tech II)

    Here is how I plan on approaching this:

    Look at any wiring diagram I can and start, one by one, finding things connected to the PCM and start unplugging them, watching for a change in the draw?

    How would you do it?

    THanks!

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, install a sound system
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    Re: PCM is staying awake causing 4.5 amp draw

    Remember that your car has RAP - Retained Accessory Power - that stays hot for about 10 minutes after you turn off the engine - and resets every time you open or shut a door............ so the fuse-pull exercise can be very frustrating until the car goes "to sleep".

  4. #3
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    Submariner409 -

    I have tried to get it to drop out of the 4 amp draw but it doesn't, even for over an hour.
    maybe my RAP is what is misfuntioning.
    Gonna do some "RAP" research

    ----------

    OK, first step: set up and see if RAP things are staying on past 10 min.

    I would post the chart from all data I am using, but I have to resize the .gif and don't know how.

    ----------

    what exactly should I try to use after 10 min. I assume the driver's seat controls?

    ----------

    driver's seat still moves after 10 min.
    pulled the RAP relay and fuse, driver's seat still moves

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    Submariner409's Avatar
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    Re: PCM is staying awake causing 4.5 amp draw

    Driver's seat is always hot, as are headlamps, interior lamps, gas door and trunk lid. RAP controls stuff like power windows, mirrors (I think), radio operation, sunroof, OnStar, others.

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    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    Thanks Submariner409, with that info, I'm gonna do a little more investigation

    ----------

    The radio thing makes it easy:
    windows down, charger on battery, key ON, radio ON, key off and out

    Radio is playing, key is out, timer is set to 10 minutes, we'll see if the radio is still playing in 10 minutes, but I'm sure it will be

    ----------

    Ok, radio was off, so RAP is working, so something else is keeping the PCM awake.

    Off to a BBQ, will work on this later.

    Does the PRND321 light stay on for you? It does for me.

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    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    OK, I'm back and working on this.

    Must not be the RAP staying on.

    Still at a draw of about 4.5 amp continuous, right after plugging the battery back in. I don't know what my next step is?

  8. #7
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    I think this might be wider than the PCM. I've got little draws all over. Ignition switch, bunch of module, stereo, amp, etc.
    I don't know how the inside of a "module" works, but, is this all symptoms of a slightly fried electrical system? Could someone have hooked up a battery wrong and done something to lots of "modules" in the car, making them draw a little power? I've also got some relays stealing power too. I might be able to figure out if the relays are leaking by swapping them with a similar one.

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    Submariner409's Avatar
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    Re: PCM is staying awake causing 4.5 amp draw

    Our cars, with RAP off, have a continuous parasitic discharge of 15 - 25 mA.

    I agree that a continuous 4.5A discharge is totally unsatisfactory.

    Do you have an aftermarket sound system/amplifier in the car ? Sound systems with sensing amps sometimes do what is happening to you.

    No, my DIC gear shift indicator does not stay lit - Key: OFF, it's off.

    .................. If this doesn't get more response here in Electrical, we might want to move the thread to Deville for more exposure .........

  10. #9
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    Thanks Submariner409
    No aftermarket installs present, although one in the past, I can see the turn on wire back by the battery.

    Before asking anyone to read through this and answer questions, I'm going to gather as much info as I can before asking a specific question. Right now I know I have draws coming from about 14 different places (mostly fuses, some relays), all seem something to do with a module. Almost a complete shut down of draws when removing the PCM BATT fuse underhood. 4.65 to .15

    I'm leaning towards two scenarios:
    1)a reverse polarity battery hook up fried stuff and is causing the draw.
    2)there is a loom somewhere, messed up, causing multiple small shorts (the wiring under the drivers seat does look as if someone was messing around)

    As is, I drive it everyday, just leave it on a charger when not in use.

  11. #10
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    I just keep posting my progress, maybe it will help someone else out in the future.

    I MAY have made a breakthrough, but it started raining and I can't confirm.

    I do know I was messing with the connectors below the driver's seat, which there are way too many wires under there, and I don't have a draw anymore.

    ----------

    Nope, false alarm

  12. #11
    rodnok01's Avatar
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    Do you have any codes? I wonder if ignition switch is not shutting off properly, can't remeber the reason th e PRndl stays lit. Either switch or IPC i believe was that issue. Just a thought.

  13. #12
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    Thanks for the idea.
    No codes, at least that apply.

    There is a reason the PRND321 stays lit? I assumed my Instrument Panel was needing repair and it wasn't related to all this other stuff. I pull the I/P fuse and it stops about .8 amp of draw.

  14. #13
    rodnok01's Avatar
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    Re: PCM is staying awake causing 4.5 amp draw

    Can't recall the reason PRNDL stays lit off top of my head(or the fix), but it has been seen around here a few times.
    It may have been related to ignition switch but I can't swear by that.
    Avaya likes this.

  15. #14
    dkozloski's Avatar
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    Re: PCM is staying awake causing 4.5 amp draw

    Has the car ever taken a swim? It sounds like a flood car.
    Don't mess with Binky Bear!


  16. #15
    Avaya is offline Cadillac Owners Fanatic
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    Re: PCM is staying awake causing 4.5 amp draw

    dkozloski: not according to records, but it sure seems like it, doesn't it

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