Bcm
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Bcm 02 Firebird (v6) having issues where the alarm is seemingly going off every time I close/open a door or bump the car a little hard (stays on even after I start the car), I've unplugged the shock sensor to no avail. Headlights pop up and down when this happens, and I've pulled the dash off to try and find an aftermarket alarm system with no results. Also can't enter programming mode as stated in a previous post. VATS has also been bypassed completey and there is no security light. I believe, based on reading from previous posts that had similar issues, that my BCM is faulty. Does anyone know where to buy a good one? Or if I even truly need a new one based off my symptoms?
Last edited by Furburd; Jun 8, 2025 at 09:25 PM.
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From: fbg, tx
I am not 100% sure but you can adjust how sensitive your alarm is on the f bodies the module should be around your spare tire area and its a box about 3x2x1 big and it has a **** that lets you change the sensitivity.
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Yes I adjusted it per the service manual, and when that didn't work, i unplugged it entirely. It made no difference.
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From: Jacksonville, FL (originally from Toronto Canada)
It is not at all uncommon for the alarm shock sensor to go bad - mostly from water intrusion because of its location under the edge of the hatch. That will usually cause extremely sensitive shock activation and even random alarms for no apparent reason. However, unplugging the shock sensor should eliminate all of those false alarms. Between the false alarms and the inability to enter programming mode, I suspect you need a new BCM.
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It is not at all uncommon for the alarm shock sensor to go bad - mostly from water intrusion because of its location under the edge of the hatch. That will usually cause extremely sensitive shock activation and even random alarms for no apparent reason. However, unplugging the shock sensor should eliminate all of those false alarms. Between the false alarms and the inability to enter programming mode, I suspect you need a new BCM.
Joined: Nov 2003
Posts: 11,328
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From: Jacksonville, FL (originally from Toronto Canada)
Well, sort of. The BCM itself is not specific to the vehicle (unlike newer vehicles where the VIN is encoded in it). All fourth generation f-bodies now use the same BCM... originally there were different part numbers depending on whether the car had the optional alarm system, but all part numbers now supersede to the same part which includes the alarm circuit. However, installing a used BCM involves finding the right resistance value to satisfy VATS. If you can get the original key with the BCM then it's easy to just do a VATS bypass using the resistance value of that key. Unfortunately, that almost never happens, so you'll have to figure out the correct value. There are 14 different values, so you'll just have to try a bypass with each one until you find the one that works.
Thread Starter
Teching In
Joined: Nov 2024
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Well, sort of. The BCM itself is not specific to the vehicle (unlike newer vehicles where the VIN is encoded in it). All fourth generation f-bodies now use the same BCM... originally there were different part numbers depending on whether the car had the optional alarm system, but all part numbers now supersede to the same part which includes the alarm circuit. However, installing a used BCM involves finding the right resistance value to satisfy VATS. If you can get the original key with the BCM then it's easy to just do a VATS bypass using the resistance value of that key. Unfortunately, that almost never happens, so you'll have to figure out the correct value. There are 14 different values, so you'll just have to try a bypass with each one until you find the one that works.
