machone03

Alright here goes. I had the ever so popular leak in the passenger side and believe I got it taken care of but now my car won't start sometimes. IF you unplug the BCM and plug it back up all is normal for a while.Service engine, service ABS, Service AH,Low fuel, Reduced engine power all flash across the DIC.

U1000hc
u1160hc
u1176hc
u1096hc

I got all of these from the DIC, BCM and HVAC showed no comm. although HVAC works. The radio doesnt work, nor does the dome lights, window controls etc. I wiggled the accordion boots, pulled them back and checked for cut/chaffed wiring to no avail. The ground on the RH side under the water drippage path looks clean(I didnt take it apart) I removed the caps off the Serial cables next to the BCM, shorting bars were in place. The only thing that seems to get the car back to a right state of mind is unplugging the BCM which is probably just like unhooking the negative and resetting it. Where do I start now!??!?!?

ajg1915

Seems like you need someone with a Tech2 that can test the BCM to see if it's damaged, etc ...

Some better shops have the Tech2 and few guys on th eforum also own them, But all dealers have them.

machone03

Forgot to add I took the BCM and took it apart and it is clean inside, pins are clean and it's dry. None on the printed circuit or any of the resistors, diodes, capactiors etc are messed up.

machone03

I borrowed a Tech 2 today and it had a few special tests which it performed/passed. however when the BCM loses communication you obviously can't do any testing with the Tech 2. When the BCM was in fail mode I commanded the door modules, seat module, etc. to do things and they all passed. I beleive it's the BCM or a power/ground issue causing it to totally go dead. I'm going to get the schematics and check for power/ground at the 3 connectors to the BCM.

ajg1915

I would check the fuse first, then the power and ground.

machone03

I checked the fuses the first time it happened. Also checked resistance at the rf kick panel connector it's less than 4 ohms so if it has corrosion, it isn't much. Also power and ground to BCM are good and showing battery Voltage. Sounds like the BCM is shot.

ajg1915

One way to check it is to hook up the tech2 and see if you access RPO codes.

Anyway, best of luck with repairs.

dgrant3830

Also check the star connector which is where the data buss connects right there to the left of the BCM. Bill's got pictures of this connector I think in the sticky.

machone03

Checked the Star connector, Buss bar is there and no corrosion/bent pins etc.

dgrant3830

I no longer have the manuals, but you'll probably need to do bench tests on the individual units. I agree that it sounds like the BCM is done. Hopefully when you pulled it out and took it apart, you diconnected the battery first otherwise its probably done for sure. When you had it apart, did you actually clean the entire thing with alcohol or electronic parts cleaner and then carefully make sure it was dry before reinstalling it? Did you insure you and it were electrically grounded, while working on it as its static sensitive? Another quick thought and I don't know the answer, does it lose the security programming once its disconnected? You might need to do the re-learn procedure to get the security to work again...I sort of doubt this is the issue in this case.

machone03

Battery was unhooked the first few times I unplugged, it didn't seem to matter if it was hooked up or not.Alldata doesn't even suggest to unhook the negative cable. When I took it apart the first time I cleaned the small area that the board touches the case with rubbing alchohol and put a dab of dielectric grease on it, as it looked like the ground had maybe been arcing, there was NO corrosion or moisture on the chipset .although I took a hairdryer on low heat to it for 3-4 minutes, and yes i grounded myself. Like you and I said it's probably the BCM I'm going to call a guy in a few minutes who had the same problem and will report back. Thanks for all the help guys!

DSM TJ

Any word on what the cause was?

machone03

Yes, there was some corrosion beside/underneath one of the relays on the BCM. I Went over it with a magnifying glass and found the discolartion, I heated up the solder and took the relay out and there was corrosion under it that was shorting two printed circuits, i took some scotch brite pad, contact leaner and a qtip, resoldered the relay and its been fine since!

dgrant3830

Very Cool and Thanks for reporting back on your fix. Its important for us so we can possibly share your fix with others.

machone03

I forgot about the thread or would have updated it sooner. Hope someone can benefit from my headache.

SilverC54me

Just fixed the same type of issue on a friends car. The components at the bottom edge of the BCM had light corrosion around them. Removed the relays and cleaned the corrosion off with a old tooth brush. Resoldered several components in this area and it is working.

Now to see if it stays stable.

Gary

machone03

Should take care of it. Mine's been great ever since.

y2kvett

The BCM on this one has a strong aluminum box around it. I don't think you can open it without bending the aluminum. Any ideas?
Thanks,
Steve

SilverC54me

Yes you have to bend the case to get to the circuit board. It is easy to bend since it is aluminum.

Gary