• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

BCM Problem?

C

campbech

New member
Having an issue with my 2005 Grand Prix GTP with some weird issues occuring.

  • Door locks sometimes work randomly
  • My remote works but my wifes' doesn't now
  • Try to remote start the car and the alarm goes off
  • Blower for the heat/cooling works sometimes
I have been told that they think the BCM is failing, sound reasonable?
 


That sounds about right. However there is a ground behind the dash almost directly behind the key switch that bolts to big cast aluminum/pot metal dash support. If that ground somehow works loose, it can and will drive you nuts trying to figure out "what the hell" is wrong??? God luck.
 
I would try unhooking the battery for 10-20 minutes and hooking it back.

The bcm may be confusing itself. did the dealer scan for codes in the bcm?
 
Michaelbm, when they scanned for codes the only code that came up was a wastegate solenoid issue with my supercharger. That is for another post.. Wonder how hard this is to replace and can I do this myself?

Ok, unhooked the battery and cleaned the posts very well. Disconnected the BCM at the same time for about 10 mins or so.

Reconnected everything and still the same issues with no heat.

Got mad I just spent 45 minutes in the cold without resolving any issues so I took out a frustration palm hit to the top of the dash and my blower for my heat came on.

Looking like maybe a ground issue after all?
 


the blower motor ground should be behind the center of the dash aproximately.. behind the radio/center stack.

I would not say its the bcm as well the bcm doesnt recognize the difference between remotes where the reciever does and holds the programming info for matched remotes.

I could certainly see the power locks not working from something as simple as a missing ground since the bcm has different grounds and stuff for different areas within the bcm such as relays.

Behind where all the radio and stuff is I have a picture in the link below that shows the ground where your blower motor comes from. Its worthwhile to check this.

http://i882.photobucket.com/albums/ac29/michaelmeade/HVACGROUND.jpg

theres another ground close to it for a few other things these grounds should be accesable if you take of the knee panel under the steering column and also the metel shield under it.

http://i882.photobucket.com/albums/ac29/michaelmeade/Otherground.jpg

I would wiggle each wire and see if any are loose.

I was just looking in alldata and one of those grounds I mentioned in the pics is shared by both the bcm for power lock switches as well as the HVAC panel ground.
If indeed the door lock switches are not working but your remote is that could potentially be a problem.

Once you get these taken care of you can see is the keyless entry problem is solved too. Did you check inside the inopertive remote yet?

As far as bcm replacements go thats the one thing you should get new which would requiere the dealer programming. Used bcm's cannot be reflashed for use in different vehicles so a used one would have to be from a car with the exact same options as yours and still need theft learing and unlocking your stock deck if you still have one like me.

However putting one in is very easy, its to the left of the steering column and you can see it if you take the dash end cap off where the door meetsthe dash.

If you had access to a cheap used one you could plug it in temporarily and verify the remote possibility the bcm is the cause of the keyless and door lock problems. but it wont let you start the car and stuff like that.
 
Last edited:
Not yet. Will try and tear the dash apart on Monday and see what I can see. Hitting the dash every few days fixes the heat and that was the major concern right now.

One more question though, where is the wastegate for the supercharger. Something easy to check? Getting a code for wastegate solenoid having issues.
 
Ok, sorry for the very late reply. I tore the dash apart tonight and re-did the ground connections behind the stereo, under the metal sheet under the steering column, as well as the chassis ground by the battery. Same issues for the most part.

Since my last posting I pulled our key FOBs apart and saw that the solder joints were broken and have since fixed them. The remote start though still alarms when you try it with either FOB.

Blower motor has been running ever since I gave it a good pounding to the dash back in December.

Door locks aren't working except for the front passenger door, and that one always works.

Kind of at a loss now.
 


BCM not communicating but appears to be working fine.

I don't get any symptoms but when I go to pull codes from the car the BCM doesn't communicate I just get the Engine Codes. Does that make sense?
 
Regarding the blower issue posted by campbech.GM has a campaign to replace "noisy" blowers. This is a warranty issue. Run a check of your VIN at the dealer and see if the blower has been changed out. I had this done on my 05 but it was still in warranty.
 
You must log in or register to reply here.
Back
Top