Diagnosing a (suspected) bcm problem with 2011 GMC sierra. Please help

[Aaron Wooten]

I have a 2011 gmc sierra and over the past 6 to 8 months I've had things keep getting worse.

 

It started out with my truck randomly showing "service stabilitrak", the abs light would come on, and "reduced engine power". I could pull over and turn the truck off for about 2 to 3 min and crank it back up and go for months.

 

After about 4 months of that it started getting more frequent, let's say once a week. After a few weeks of that it got even more frequent doing it almost every day. While all this was happening (6 monthsish") twice while I was driving all my dash lights would flash and locks would lock and unlock multiple times, I would pull over turn the truck off for a few minutes and I'd be good to go. But this was a rare occurrence, happening months apart. 

 

About 2 months ago (5 months into this whole problem) the airbag light started randomly coming on and off also.

 

I did some research and thought it could be the throttle body but with both of those issues going on I read that it could be the body control module also. 

 

I finally took it to the dealership and after looking they said they want to change the battery cables and battery because they weren't any good (which makes sense, I always had build up on the terminals and the truck would go dead pretty quick) and they said that could be causing the other issues because the the bcm might not be getting enough power. So they changed the cables and put a new battery in. I left and within 2 days I had the reduced engine power, stabilitrak and abs showing again.

 

The flashing dash light and doors locking and unlocking has not came back.. (maybe the battery fixed that issue??)

 

I called and they wanted me to bring it back so I did and they ran the engine light code and  it showed p2138 which is "Throttle/pedal Position sensor/ switch "D" "E" voltage correlation". I didn't have the $ at the time to spend at the dealership so I left.

 

I drove it the week after Christmas with the reduced engine power happening a couple times. 

 

I bought a throttle body this week and put it on and it drove fine for 2 days... But the reduced engine power, stabilitrak, abs light thing is back today!.. along with a brand new issue showing up! Lol.. it now is showing "service charging system" and my battery gauge is at 9. 

 

Does anybody have any ideas of what it could be? My gut says the BCM but I don't know what I'm talking about. Any help would be much appreciated.

 

And sorry for the wall of text

[silveradosid]

have the alternator load tested

[Aaron Wooten]

I'm at the shop now. The alternator is bad. Hopefully this fixes some problems. I just have a feeling this won't fix the reduced engine power issue. Finger crossed though

[HawkScot]

A few years ago, I had some intermittent problems on the way home from camping.. hit a bump and the doors locked and unlocked, stabilitrac light came on, then all good.. checked codes and it pointed to transmission communication. Ended up being mice had got into wiring harness under engine cover and after repairing wiring, no further problems.  I would suggest a careful visual inspection of wiring, make sure you don't have a rodent problem.