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Fried my BCM- Any help appreciated!

This is a discussion on Fried my BCM- Any help appreciated! within the Stereo and Electronics forums, part of the General Help category; Let me preface this by saying I was a dolt and screwed up. While bolting my dash back in (changed ...

  1. #1
    Member bberretta's Avatar
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    2000 TA Firehawk 0041/742

    Fried my BCM- Any help appreciated!

    Let me preface this by saying I was a dolt and screwed up. While bolting my dash back in (changed out the entire AC system and swapped out my old, cracked dash for a new to me not cracked dash) I caught a wire, grounded it out and cooked the BCM. I guess if I'm going to screw up, I'm going to do it right.

    I've tried to get a junk yard BCM and do the relearn process but no luck. My new BCM will arrive soon but I'm not sure if that is 100% of the problem. Everything works with the junk yard BCM except the car will not turn over. Turn the key and the only light that comes on is the Security one. The "starter" fuse under the hood is getting power when the ignition is turned but the solenoid is not getting any power so the stater is not turning over.

    Here's my question: does this sound like the BCM only or have I royally screwed something up and need to start digging further? Is the starter fuse prior to the starter relay and if so, is this why the car will not start (my understanding was that the BCM cut the ground to the starter relay causing the car to be unable to start if the BCM did not recognize the proper resistance).

    Thanks for any help!
    2000 Pontiac Firehawk #0041 of 742

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    Your friendly policeman FinZ28's Avatar
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    The security light sounds like a VATS issue. There is a write-up on here on how to bypass it. Might be worth looking into.
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    Senior Member theorangeguy's Avatar
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    Quote Originally Posted by FinZ28 View Post
    The security light sounds like a VATS issue. There is a write-up on here on how to bypass it. Might be worth looking into.
    BINGO! Time to get a resistor and go to town................

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    Member bberretta's Avatar
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    The only problem with the VATS bypass is that the resistance is stored in the BCM and I do not know the resistance of the junk yard BCM. I guess I could try all 15 to see which one it is but hopefully the new BCM will learn my key and I'll be good. Thanks for the help, guys!

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    Senior Member theorangeguy's Avatar
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    Quote Originally Posted by bberretta View Post
    The only problem with the VATS bypass is that the resistance is stored in the BCM and I do not know the resistance of the junk yard BCM. I guess I could try all 15 to see which one it is but hopefully the new BCM will learn my key and I'll be good. Thanks for the help, guys!
    I always thought the resistance was in the key, which is what tricked the system into thinking the correct key is engaged? I could be wrong tho...I have read in the past that you can disable it @ the PCM level and the car will start with no issues as long as its a vats problem BUT I have never done that and I dont know anybody personally who has...Some people say that since its the BCM that communicates with the PCM you can tune it out, others say that it cant be done............
    Last edited by theorangeguy; 06-04-2013 at 07:53 AM.

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    Member bberretta's Avatar
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    The resistor is in the key, but the setting is stored in the BCM. When you install a new BCM it is open and learns the resistance from the key. The relearn sequence (of which I've tried about four different combos) is supposed to re-open the BCM so that it relearns the new resistance of the chip in the key.

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    Senior Member theorangeguy's Avatar
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    Quote Originally Posted by bberretta View Post
    The resistor is in the key, but the setting is stored in the BCM. When you install a new BCM it is open and learns the resistance from the key. The relearn sequence (of which I've tried about four different combos) is supposed to re-open the BCM so that it relearns the new resistance of the chip in the key.
    Found this while I was searching...

    "You can jump the purple wires together and just bypass the BCM entirely if you want. The bcm just controls the actual starting solinoid in the vats system. Then sends out a password to the ecm to allow fuel. If you shut off the pcm vats, then it will run as soon as it is cranked.. It is simple to jump the right wires to make it work.. As long as the ecm has been programmed of course..."

    Dont know if this will help you in your situation since your BCM is new, but here is the diagram that was attached to it. This is for an 02 Fbody...



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    Member bberretta's Avatar
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    That does help out, thanks for posting those! I guess my question is at the underhood relay/fuse box and the purple wire going to the starter solenoid. When I try to crank the car, the fuse goes hot which tells me that the power is coming from the ignition switch but it is not sending power to the solenoid. The 5/PPL wire is the one in question from the top image. Is there a fusible link on that wire that I could have possibly fried as well? If I run a wire from the fuse block to the solenoid the car will start and run but the security light stays on. The only thing I can think is that I am either 1) bypassing the starter relay or 2) bypassing a fried fusible link and I still have VATS issues.

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    Senior Member theorangeguy's Avatar
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    Quote Originally Posted by bberretta View Post
    That does help out, thanks for posting those! I guess my question is at the underhood relay/fuse box and the purple wire going to the starter solenoid. When I try to crank the car, the fuse goes hot which tells me that the power is coming from the ignition switch but it is not sending power to the solenoid. The 5/PPL wire is the one in question from the top image. Is there a fusible link on that wire that I could have possibly fried as well? If I run a wire from the fuse block to the solenoid the car will start and run but the security light stays on. The only thing I can think is that I am either 1) bypassing the starter relay or 2) bypassing a fried fusible link and I still have VATS issues.
    It looks like you are bypassing the starter relay based on the diagram and what you are describing. Im not sure about any links between the fuse block and the solenoid tho.

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    Member bberretta's Avatar
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    That's exactly where I'm confused- I guess the fuse is before the relay on the circuit which would be why the fuse would go hot. If the BCM isn't grounding the relay due to the VATS issue then even if the fuse goes hot, without a ground the relay wouldn't switch over and the solenoid wire wouldn't be hot. I'm just guessing and do not claim to know anything really, but I guess I'll know a bit more when the new BCM gets here later today.

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    Senior Member theorangeguy's Avatar
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    Quote Originally Posted by bberretta View Post
    That's exactly where I'm confused- I guess the fuse is before the relay on the circuit which would be why the fuse would go hot. If the BCM isn't grounding the relay due to the VATS issue then even if the fuse goes hot, without a ground the relay wouldn't switch over and the solenoid wire wouldn't be hot. I'm just guessing and do not claim to know anything really, but I guess I'll know a bit more when the new BCM gets here later today.
    Im curious to see what it does with the new BCM installed.

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    Member bberretta's Avatar
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    You and me both! I'm going to pull the junk yard BCM and test to see if the car will start with the jumper wire (which is similar to what you are describing with jumping the purple wire). I know with the fried BCM the starter fuse would go hot but nothing else would work.

  13. #13
    Member bberretta's Avatar
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    Dropped the new BCM in and it started right up. The junk yard BCM must have been bad which explains why it wouldn't relearn. So yes, you can get the car started even if the VATS is bad by simply running a wire from the starter fuse to the solenoid on the starter. The BCM stops the starter by stopping the starter relay from grounding. So, if your VATS goes bad, you can MacGyver your way home with six feet of wire.

    Lesson learned- just because you think you have all the wires tucked and taped up before you bolt the dash back in, it doesn't mean you do. Another $180 lesson learned...

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    Senior Member theorangeguy's Avatar
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    Good to hear that its back up and running!

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