PRND321 Light Always On
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Electrical Technical Information Discussion, PRND321 Light Always On in Item Specific Cadillac Discussion; Hello everyone. I am new member to this forum as I don't own a Cadi but my brother is the ...
  1. #1
    cmm491 is offline Cadillac Owners Member
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    PRND321 Light Always On

    Hello everyone. I am new member to this forum as I don't own a Cadi but my brother is the owner of a 2002 Cadillac Deville that he purchased a few months ago. There was a new battery installed in the car but that battery is pretty much toast now due to a parasitic draw issue the car is having. I am posting here to see if anyone can help me understand the issue a little bit better as I told him I would try to help him out.

    Knowing all the electronic features of these things, I am sure any small unordianary draw on the battery will cause the vehichle not to start. I am going to call the PRND321 (the gear display) is always on. Even if you take the key out of the ignition, that display remains on. I can only assume that something tied with this is the cause for the draw on the battery.

    I searched and searched and could not find anything on this issue but a point in the right direction would be great. Remember, I have no idea how the system works. What I did find is that it could be the ignition system, like a switch or something?

    Thanks for your help

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  3. #2
    JimD is offline Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    Quote Originally Posted by cmm491 View Post
    ....There was a new battery installed in the car but that battery is pretty much toast now due to a parasitic draw issue the car is having.
    All modern cars place a very light load on the battery when the vehicle is closed, locked and unused. Typically, a serviceable battery will support that load for at least 7 days and still have the capacity to crank the engine.
    Knowing all the electronic features of these things, I am sure any small unordianary draw on the battery will cause the vehichle not to start. I am going to call the PRND321 (the gear display) is always on. Even if you take the key out of the ignition, that display remains on. I can only assume that something tied with this is the cause for the draw on the battery.
    Sitting in the driver's seat with the doors closed, removing the key will not necessarily turn all accessory items OFF. But opening the door will shut (almost) everything down. You can demonstrate this to yourself by listening to the radio with the door closed and key removed and then opening the door and observing the results.

    GM/Cadillac typically calls most of the above the Retained Accessory Power (RAP) system.

    Bottom line is you need to know the battery load AFTER the RAP system times out. If you are electronics savvy enough to measure battery current load (requires ammeter and an understanding of what the ammeter is indicating), I can detail my procedure for measuring "parasitic" load.

  4. #3
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    Thank you for your response. I am familiar with the RAP as I drive an '06 Grand Prix. The gear display not only doesnt shut off beyond the RAP time, but the only time it shuts off is if the battery drains completely or the terminals are taken off the battery itself. As soon you hook the terminals back up, that gear display comes right back on. Of if the battery is dead a boost is needed to start the vehicle, as soon as the cables are hooked up, the gear display comes on.

    I do have some electronics knowledge but I don't have an ammeter or a multimeter currently but if you could plate a link that will get the job done ill be game to get one. I don't wanna go overkill on more features than I would need.

    But my bigger problem right now is the battery. I tried charging it but it is completely dead Andy charger won't charge it. I don't know if the battery can even hold a charge any longer. I do want to get a new battery but at the same time I don't want to waste money on it until I'm certain I'm on the right path.

    I'd love those steps to do your test and any other suggestions you might have. Thanks again!

  5. #4
    JimD is offline Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    Quote Originally Posted by cmm491 View Post
    ....The gear display not only doesnt shut off beyond the RAP time, but the only time it shuts off is if the battery drains completely or the terminals are taken off the battery itself.
    It is possible the internal logic in the Instrument Panel Cluster (IPC) has failed in such a way as to prevent the PNRD321 display from shutting off.

    You can test the theory by removing the 10A fuse labeled IP in the underhood fuse box. That should accomplish the same thing as removing a battery cable.
    I do have some electronics knowledge but I don't have an ammeter or a multimeter currently but if you could plate a link that will get the job done ill be game to get one. I don't wanna go overkill on more features than I would need.
    With my background, I can't imagine not having several multimeters at my disposal. But that's me.
    For a consumer grade meter, I suggest Lowe's has a selection of both analog display as well as digital display multimeters for less than $100. The critical function (again, that's me) would be the ammeter display capable of handling at least 10A; a 20A capability would be more than twice as desirable.

    A Radio Shack or drug store $10 multimeter is a waste of money (in my opinion).
    But my bigger problem right now is the battery. I tried charging it but it is completely dead Andy charger won't charge it. I don't know if the battery can even hold a charge any longer. I do want to get a new battery but at the same time I don't want to waste money on it until I'm certain I'm on the right path.
    Long term there is no way around buying a serviceable battery. You can do the IPC testing I mentioned above with a decent battery charger connected to the battery connected to the vehicle.
    I'd love those steps to do your test and any other suggestions you might have. Thanks again!
    Respond here when you have an multimeter capable of displaying 10A and I will do the rest of the typing.

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    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    i purchased a new battery since it needed it anyways but i still need to get a multimeter. the car has been sitting for a little while so i wanted to get it on the road for a little while, which i did. i pulled the 10A fuse from under the hood so the gear display is off. will try to turn the car over in the morning see how it goes. i will pull the battery tomorrow as well.

    hopefully tomorrow i will be able to get a multimeter.

  7. #6
    JimD is offline Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    Keep us informed.

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    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    well, after sitting overnight, it started up this morning. i only let it run for a min or two as i had to go to work. but after sitting all day, i tried starting it after work and nothing. My charger only showed around 4 volts from the battery... this is all with the 10A IP fuse removed.

    i took the battery out and i have to charge it up but i need to get some side post leads to hook my charger up to it. I could hook it back up to the car and charge it but i am not sure if the draw on the battery would damage it while charging. unless that would act just like the alternator would, then i will do that if it is okay.

    I am borrowing my friends multimeter so i am going to try and go from there with your direction.

    Thanks again!

  9. #8
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    I have the battery charged up and the multimeter

  10. #9
    JimD is offline Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    Quote Originally Posted by cmm491 View Post
    I have the battery charged up and the multimeter
    Close all the doors and the trunk. Place the ignition key in your pocket. Open the RR door to access the battery position and flip the door latch (in the door) so the vehicle systems sense that the door is closed.

    Install the battery in the car and connect the positive battery cable to the positive battery terminal.

    Set the multimeter controls to read DC AMPS and using alligator clips, connect the meter in series between the battery negative terminal and the negative cable. Make certain the alligator clips have a physically secure grip on the connections.

    Observe the meter current display for 11 or 12 minutes:
    Initial draw when meter first connected = 4 amps (plus or minus a little)
    ET 30 sec's; draw falls to 550 ma
    ET 90 to 120 sec's; draw fluctuating from 500 ma to 700 ma
    ET approximately 3 minutes; stable at 200 ma
    ET 10 minutes; drops to 30 ma or less forevermore.

    The Retained Accessory Power (RAP) is supposed to time out at 10 minutes. After 10 minutes, if you observe current flow of much more than 30 ma, there is a faulty module or wiring situation somewhere. The first suspect would be any aftermarket equipment that might have been installed at some time during the life of the car.

  11. #10
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    thanks for the info. I will try that when I can. There are no aftermarkets on the car but I suppose I will start pulling fuses and going that route.

  12. #11
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    Quote Originally Posted by JimD View Post
    Close all the doors and the trunk. Place the ignition key in your pocket. Open the RR door to access the battery position and flip the door latch (in the door) so the vehicle systems sense that the door is closed.

    Install the battery in the car and connect the positive battery cable to the positive battery terminal.

    Set the multimeter controls to read DC AMPS and using alligator clips, connect the meter in series between the battery negative terminal and the negative cable. Make certain the alligator clips have a physically secure grip on the connections.

    Observe the meter current display for 11 or 12 minutes:
    Initial draw when meter first connected = 4 amps (plus or minus a little)
    ET 30 sec's; draw falls to 550 ma
    ET 90 to 120 sec's; draw fluctuating from 500 ma to 700 ma
    ET approximately 3 minutes; stable at 200 ma
    ET 10 minutes; drops to 30 ma or less forevermore.

    The Retained Accessory Power (RAP) is supposed to time out at 10 minutes. After 10 minutes, if you observe current flow of much more than 30 ma, there is a faulty module or wiring situation somewhere. The first suspect would be any aftermarket equipment that might have been installed at some time during the life of the car.
    I haven't had a chance to begin testing the amp/ma draw on the battery with the RAP yet but after thinking about the steps I had a couple of questions.

    Currently the car is sitting with no battery installed. Would I need to:

    1. install battery with both the + and - terminals so the car has power
    2. open the passenger rear door and flip the latch
    3. then turn the ignition key so the RAP functions then turn switch to off and remove the key
    4. then proceed to test?

    or am i overthinking that.

  13. #12
    JimD is offline Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    Quote Originally Posted by cmm491 View Post
    ....or am i overthinking that.
    Yes.

    Simply completing the battery connection with the ammeter will set a series of tests in motion. You will hear some relays being switched ON and OFF.

    The critical part is the final ammeter reading after 10 minutes.

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    rodnok01 is online now Cadillac Owners Connoisseur
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    Re: PRND321 Light Always On

    I know it's a different model, but the only time PRNDL light comes on with nothing else is when key is slightly turned, not quite to the run position, when turned to run everything else comes on. Possibly a flaky cylinder and it's reading partially on?

  15. #14
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    Quote Originally Posted by rodnok01 View Post
    I know it's a different model, but the only time PRNDL light comes on with nothing else is when key is slightly turned, not quite to the run position, when turned to run everything else comes on. Possibly a flaky cylinder and it's reading partially on?
    i dont have much background or knowledge on this but my gut feeling says it is either the instrument panel or the ignition switch. but i dont know if the PRNDL portion is connected to the instrument panel if it turns out to be faulty logic.

    thanks for the info.

  16. #15
    cmm491 is offline Cadillac Owners Member
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    Re: PRND321 Light Always On

    Quote Originally Posted by JimD View Post
    Close all the doors and the trunk. Place the ignition key in your pocket. Open the RR door to access the battery position and flip the door latch (in the door) so the vehicle systems sense that the door is closed.

    Install the battery in the car and connect the positive battery cable to the positive battery terminal.

    Set the multimeter controls to read DC AMPS and using alligator clips, connect the meter in series between the battery negative terminal and the negative cable. Make certain the alligator clips have a physically secure grip on the connections.
    I installed the battery with the positive terminal and finished the circuit with the multimeter. I was getting a reading of about .01-.02 amps from the moment I connected the multimeter. So i switched to ma's and it was reading around 20 ma's consistently for a long while. Hmm right? (the 10A fuse for the IP was still removed at this point)

    I still have a gut feeling it is something with the ignition system so for the heck of it I hooked the negative terminal to the battery (remembered the IP fuse was not in so I put that back in) and started the vehicle up and let it run for a few mins. I flipped the door latch on the RR door and shut the car off from the back seat and removed the negative terminal to hook up the multimeter. It was reading 4+ A at intital hookup. It eventually settled to 3.83 A. I left it alone for about 30 mins and it held at 3.83 amps. So yeah, that's a pretty significant draw.

    I started pulling the mini fuses under the hood first and only one adjusted the amps, that was the IP fuse and it dropped the draw about 1.53 amps I proceeded to the fuse box under the seat and here were the results that dropped the amps:


    -1.53 A -- removing IP minifuse (mentioned above)
    -1.37 A -- removing minifuse 21 'Audio'
    -0.90 A -- removing minifuse 29 'Ignition Switch'
    -0.40 A -- removing minifuse 2 'HVAC Battery'
    -0.07 A -- removing minifuse 5 'Driver Door Module'
    -0.05 A -- removing minifuse 25 'Passenger Door Module'
    -0.05 A -- removing minifuse 18 'Right Rear Door Module'

    The door modules seem fine to me. Could the ignition system not be allowing the system to shut off the radio and instrument panel? Or maybe the RAP is having an issue?

    When removing the minifuses, I did notice that micro relay #51 'Interior Lamps' and mini relay 58 'Cigar Lighter' were quite warm. Warm enough to cause some discomfort on my finger if left there for a few seconds. Is that normal? I was not sure if I was able to or even how to properly remove the micro relays, circuit breakers or mini relays. If i should check these too, please advise how.

    I know the manual says to have the vehicle serviced if a maxifuse blows but am I able to pull those as well to check the amp draw?

    Lastly, when I was pulling the fuses from the rear seat box, I noticed every few minutes that I could hear a click in the dash area of the car. I don't know where it was coming from.

    Any and all help is greatly appreciated. Thanks for your assistance!

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