Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!
1 - 6 of 6 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 · (Edited)
I had two batteries that were due for replacement and started to drag when starting the truck. I got in the truck to go to work but the batteries were too weak and it wouldn't start, I jumped it with my Yukon, no issue, started right up and ran fine. The truck was parked for two days and after work I had to get a jump it to get home. When I started driving I noticed that several components that are run by the BCM were not working. No power windows, door locks, ac compressor, gauges, factory speakers, and I'm sure other things. I got the truck home and replaced the batteries. Before connecting the batteries I cleaned all the cables. Now, the truck will crank and turn over but will shut off after about 1 second. I don't think it's the theft deterrent system because if I pull the ECMB fuse, I can start the truck and it will run but still no gauges, locks, power windows, etc. After stopping and shutting off the truck I need to pull the fuse to get it to run each time. I am thinking that I fried the Body Control Module at some point. I have checked all wires and grounds and nothing is damaged. I am getting power to the BCM on all of the 12v wires and and it's grounds are intact. I took the truck to my mechanic who has a Snap On scanner and it was not able to connect. Before I throw a part at it I wanted to see if anyone else has had the same problem, if anyone has any suggestions and if I am on the right track. Any help is appreciated.
 

·
Registered
Joined
·
4,370 Posts
. I took the truck to my mechanic who has a Snap On scanner and it was not able to connect.
Not able to connect to which modules?

Your truck is a series of computers and sensors and modules that all need to communicate with each other. If those communications circuits are disrupted, the result is no communications, and thus problems. You need to solve the communication problem. Don't decide that it's the BCM that is the solution until you have the proof.

Before connecting the batteries I cleaned all the cables.
Both ends? Did you test the ground from the firewall to the engine block? That is often a problem that will cause many of your symptoms.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #3 · (Edited)
Not able to connect to which modules?

Your truck is a series of computers and sensors and modules that all need to communicate with each other. If those communications circuits are disrupted, the result is no communications, and thus problems. You need to solve the communication problem. Don't decide that it's the BCM that is the solution until you have the proof.


Both ends? Did you test the ground from the firewall to the engine block? That is often a problem that will cause many of your symptoms.
Copy that. No I didn’t clean both ends, just the connections at the batteries. I’m out of town for a couple days so I will get back on it at the end of the week. As for the the scanner not connecting, is it possible for the scanner to connect if the BCM is bad? I took a snap shot of the beginning of a procedure which I believe is in line with what you are saying about figuring out the connectivity problem. When we connected the scanner it would power up but would not communicate with any of the computers. The bad thing is I don’t have the greatest access to my mechanics scanner. In the service manual that I have, there is a procedure for a multimeter, what’s your opinion on that?
1091002
 

·
Registered
Joined
·
4,370 Posts
ALLDATADIY is where I get my information, or at least most of it. Before going any further, I would make sure the DLC has power and grounds. Power comes from the cigar lighter fuse. Wiring diagrams in the Electrical Manual are available here: GM UPFITTER - Body Builder Manuals
 

Attachments

·
Registered
Joined
·
10 Posts
Discussion Starter · #5 ·
Problem is fixed. I was out of town for 3 days and when I got back and went out to the truck to continue diagnostics, the two new batteries were dead. I immediately knew that I needed to chase down a power draw. I charged the batteries and then started to check all possible culprits. I noticed that my fog light switch was not completely out. I pushed it in and it stayed stuck in as if the grease inside was sticky. I pulled the panel off, pulled off the switch and disconnected it. I then tried to start the truck and same thing, cranked and turned over but then shut off. I then removed the cables from both batteries for about thirty minutes. Re-installed the cables, cranked over the truck and everything was back to normal. I pulled up the fog light circuit and my theory is that the fog light switch must have not been able to fully ground or open since it was hanging up which caused the BCM to enter some sort of safe mode, luckily, cycling the power was enough to reset it after removing the bad switch. Thank you Ron for the effort.
 
1 - 6 of 6 Posts
Top