BCM failure and diagnosis

[stix]

The BCM on my 08 Alpha is being replaced. A symptom going in for repair was non-functioning rear taillight “fast flash”. I don’t know yet the cause of BCM failure but the web MD of forums has be a bit concerned.

I think I have narrowed to two likely culprits
1) Water damage from sunroof drain clog
2) Aftermarket LEDs (interior and rear) without load resistor (remain installed in vehicle)

Is there any way to determine the cause of the failure of the BCM? I have read that the low voltage LED’s can throw enough codes that they can permanently disable the BCM and can certainly understand that electronics don’t much care for water.

Any feedback is greatly appreciated.

Cheers!

 

[amrg]

You dont mention if you removed the LEDs and replaced em with regular lights....

 

[stix]

You dont mention if you removed the LEDs and replaced em with regular lights....

the culprit rear light assemblies were switched back to OEM, but the issue remained with the passenger rear not functioning. running lights = yes. turn/brake = no. Repair shop says bad BCM.

The other LEDs (interior and front turn signals) were working fine, remain installed

 

[speedy]

Factory tow package? Check wiring between muffler and rear bumper for melted wires. We had this problem a few years back with similar symptoms. Still fried the BCM

 

[stix]

Factory tow package? Check wiring between muffler and rear bumper for melted wires. We had this problem a few years back with similar symptoms. Still fried the BCM

yes - factory tow package...checked that before taking to $hop....looked OK

 

[amrg]

How about you change all lights to stock and see? Still cheaper than a bcm

 

[cgalpha08]

Mine was fried when i bought my 09, didn't notice it until after i had signed the bill of sale though lol anyway my symptoms were the dome lights didn't work, and the door mirrors wouldn't adjust the with switch. Tried the normal fuse checking and changing out the switch etc. Dealer confirmed it was a bad BCM, not sure what caused it to go bad, no sign of water damage so who knows.

 

[stix]

How about you change all lights to stock and see? Still cheaper than a bcm

I do appreciate the feedback - yes - had thought of that, and might do that eventually. I do trust the $hop to a degree (when they say the BCM is shot) and not sure that the problem would fix itself considering the rear lights, which were the only ones affected, had been moved back to OEM.

If there was a way to determine the cause of the BCM failure, I could attempt to prevent the issue from happening again. Obviously, the sunroof drain lines need to remain cleared, but if I dont need to move back to OEM lights all around, would prefer not to.

 

[f5moab]

Doubt if it was the LEDs, I had them in my H3 for years and only added load resistors for the flashers.
Also, cannot figure out how a large number of codes would destroy the BCM.
I would suspect water damage from a leaking sunroof drain cause the BCM, unlike a PCM or ECM/TCM is not designed to be subjected to water. And water and electronics don't mix well and cause a lot of problems.
However, like all things electronic, they sometimes just go wacko for no apparent reason.

 

[amrg]

Ive recently stumbled across a thread of a russian guy going through the Lengths of relocating his bcm higher up. Talk about wiring!

https://www.drive2.ru/l/478836215458562279