BCM gremlins

CHIKNMN · September 28, 2022

03 Silverado LS Extended Cab z71.
I purchased the truck used. It came with electronics issues. What I’m dealing with now is BCM related. With every hard reset came a different issue. E.G interior lights staying on while driving - not coming on at all - working normally, driver door control cluster dead - restart, come back on, 4x4 indicator light showing in neutral as I’m driving, next time normal, automatic climate control running blower motor on high continuously, etc.

I purchased a remanufactured BCM. Now the locks close as soon as I put in drive instead of 10 MPH as before and when I put it in park the passenger side unlocks and the 2 seconds later the driver’s side but sometimes neither unlocks or just the passenger side.

i called the re-manufacturers and they said it must be a ground issue because they do a vigorous testing of the modules before being shipped due to VIN matching. Will not replace it.

Anyone have experience with these problems?

newdude · September 28, 2022

4 hours ago, CHIKNMN said:

03 Silverado LS Extended Cab z71.
I purchased the truck used. It came with electronics issues. What I’m dealing with now is BCM related. With every hard reset came a different issue. E.G interior lights staying on while driving - not coming on at all - working normally, driver door control cluster dead - restart, come back on, 4x4 indicator light showing in neutral as I’m driving, next time normal, automatic climate control running blower motor on high continuously, etc.

I purchased a remanufactured BCM. Now the locks close as soon as I put in drive instead of 10 MPH as before and when I put it in park the passenger side unlocks and the 2 seconds later the driver’s side but sometimes neither unlocks or just the passenger side.

i called the re-manufacturers and they said it must be a ground issue because they do a vigorous testing of the modules before being shipped due to VIN matching. Will not replace it.

Anyone have experience with these problems?

The BCM and the Body Relay Block (behind your left foot under the dash) share a common ground it appears, ground G203. G203 is located under the top of the instrument panel, near where the A pillar meets the firewall. The relay block also contains a ground bus.

Check your ground, check the ground wires out of the BCM if possible as well. Pin B6 in connectors C2 and C3 at the BCM are the ground wires., black wire white stripe. Ground wire from the relay block is pin C5 connector C1 and is the same ground circuit that the BCM uses, both going to G203.

If indeed the BCM is bad, my guess is the remanufacturer wants to see some sort of documented diagnosis from a repair shop to support replacing the BCM.

Edited September 28, 2022 by newdude

CHIKNMN · September 28, 2022

4 hours ago, newdude said:

The BCM and the Body Relay Block (behind your left foot under the dash) share a common ground it appears, ground G203. G203 is located under the top of the instrument panel, near where the A pillar meets the firewall. The relay block also contains a ground bus.

Check your ground, check the ground wires out of the BCM if possible as well. Pin B6 in connectors C2 and C3 at the BCM are the ground wires., black wire white stripe. Ground wire from the relay block is pin C5 connector C1 and is the same ground circuit that the BCM uses, both going to G203.

If indeed the BCM is bad, my guess is the remanufacturer wants to see some sort of documented diagnosis from a repair shop to support replacing the BCM.