From everything I understand, you cannot simply "trade" the BCM out. It needs programmed for your car (programmed for your option codes).

 

Yes it needs to be programmed for both options/courtesy features but also security/passlock. You can do the key on relearn for passlock to allow the car to start and drive. When I put in a new BCM to test and just relearned passlock some features like the radio, footwell lights, etc didn't work without it being dealer programmed with the connivence features from the sticker in the trunk. Even though it never got programmed by the dealer it did help me rule out the BCM as my issue

 

I would seriously consider checking your grounds before rushing out and spending money on a BCM. GM has issued several TSBs about this problem relating to other models and after the grounds were cleaned all the symptoms went away.

 

I do not intend to change the BCM.

I intend to disconnect it, check/clean the connectors, and reconnect it.

Will any relearn/reprogram procedure still be required ?

Thank you guys

 

That makes sense, I will check grounds first.

Thank you

 

Update.

So about 6 weeks ago, I checked the grounds.

Transaxle ground was nice and clean. Still, I unplugged it, cleaned it and applyed dielectric lubricant to it before plugging it back.

But chassis ground was another story...

First I had a hard time unscrewing it. The bold was all rusted. Since it was on a sunday, I couldn't get a new bolt so I cleaned it on the bench grinder wire brush. I cleaned the hole as weel as I could, applyed dielectric lubricant and screwed the bolt back.

Then weeks passed. The problem didn't happen for a month (it happened 2 or 3 times a week before). Then 2 weeks ago, driving in heavy rain, it happenned again. But only once, and didn't happen since.

So I'm confident this ground might have been the problem since the beginning. As soon as possible, I will replace the bolt.

Thank you guys for all your advice.

 

Good to hear a relatively inexpensive repair appears to have resolved the problem.

 

i am having the exact same issue with my 2005 monte right now. I too have a strong suspicion all my issues root back to a grounding issue as all this has happened after a month of straight rain in my area and i see you were able to solve yours by cleaning your grounds.
excuse me for sounding like a newb (****) but where do i find the air box and the transaxle grounds and where did you find your chasis ground bolt.
i have a similar thread in this forum, but it seems to be you have first hand experience with the issue and i would love to pick your brain

 

You'll need a flashlight to see the transaxle ground. Look way down throught the space between the air box and that big radiator hose :



Chassis ground is under that wire harness close to the battery :



Hope this helps

 

thanks for the speedy reply panpan and the pictures were great. i actually just went out and followed the wire from the negative battery terminal. i disconnected and checked it out, it was in good shape but i used a wire brush anyway, but i didnt have any luck. so i guess im just gonna keep checking different spots.
one thing i did notice is that my battery is only at about 10 or 11 volts before starting the car, and once the engine is running its jumps up to about 13 or 14 volts. but i dont see why a low battery voltage would be throwing communication codes

is there any other grounds you checked. i think i found one under the dash near the ebrake, i cleaned that one up as well.