I suspect BCM... thoughts?

[George Owens]

Unfortunately no. I thought I had it, but then driving last week the whole thing happened again. All gauges to 0, multiple error codes, reduced power and stuck in 2nd gear until I disconnected the battery cable again.

I’ve changed the ecm, bcm, terminal resistor, battery, negative battery cable, mega fuse

I’m tryna add videos so you could possibly see if yours is doing the same but don’t know how

 

[Fless]

I’ve changed the ecm, bcm, terminal resistor, battery, negative battery cable, mega fuse

I’m tryna add videos so you could possibly see if yours is doing the same but don’t know how

Videos need to be hosted on a third party site (YouTube, etc.); then post the link to the video into your message on TYF.

 

[TrybalRage]

I've changed the BCM, Drivers seat memory module, replaced the negative battery cable, added grounds, battery, new alternator... checked and cleaned every ground on the vehicle, checked and applied dielectric grease to every connector for the modules on the canbus plus the main splice connectors under the hood. Inspected the low speed splice packs for corrosion. Checked wiring at all known chafe points. Pulled main fuse box and left IP box to check for corrosion and apply dielectric grease there as well.

Tech2 will show that everything is fine... until it's not. Then there's no communication until I reset the power via battery cable. At this point I think it's just one of the modules randomly freaking out internally throwing the whole network out. Unfortunately when it happens it's never at a good time for me to do a diagnostic of the condition, I need to reset it and go.

 

[George Owens]

This is what it does when I don’t have the range device plugged in

This is what it does when I DO have the range device plugged in

Now when I don’t have it plugged in and it acts up I plug in the range device while driving and it seems to reset it, I unplug it again and it acts normal for the time being

 

[Fless]

One thing to note about these more modern trucks that have a variety of modules is that each module may have its own dedicated ground pin in its harness. Gone are the days of the device's mounting connection carrying the ground through the frame or the body of the truck.

So wiring diagrams are mandatory to track down where they're supposed to be getting their ground. Just adding multiple grounds doesn't always mean anything to the module that's lacking a good ground.

 

[TrybalRage]

This is what it does when I don’t have the range device plugged in

This is what it does when I DO have the range device plugged in

Now when I don’t have it plugged in and it acts up I plug in the range device while driving and it seems to reset it, I unplug it again and it acts normal for the time being

Your first video is what mine does when it acts up while driving. Sometimes it happens while it's sitting, however, and when that happens I get a no-crank condition.

 

[George Owens]

Your first video is what mine does when it acts up while driving. Sometimes it happens while it's sitting, however, and when that happens I get a no-crank conditio

Your first video is what mine does when it acts up while driving. Sometimes it happens while it's sitting, however, and when that happens I get a no-crank condition.

Forgot to add the doors unlock lock too

 

[petethepug]

Damn nice info and thorough data on the troubleshooting. While reading blogs to put me to sleep I ran into a post where a guy had an issue similar to this from the CAN BUS lines.

Apparently the 5V line is run in series so that if one loses communication, everything downstream fails too. He found a CAN BUS line that was frayed at the end of the series, repaired it and all the modules were shaking hands again.

 

[TrybalRage]

Damn nice info and thorough data on the troubleshooting. While reading blogs to put me to sleep I ran into a post where a guy had an issue similar to this from the CAN BUS lines.

Apparently the 5V line is run in series so that if one loses communication, everything downstream fails too. He found a CAN BUS line that was frayed at the end of the series, repaired it and all the modules were shaking hands again.

Yeah it's been a pain trying to find the issue. What's so weird is if I immediately disconnect and reconnect the battery, all is fine. I've been inspecting the wiring everywhere I can, repaired one section that was causing a different problem.

My codes pop on both the high-speed and low-speed networks. There is one common denominator... the VCIM (onstar) module. Both networks go through it. I may just try and find a used one to swap in and see what happens. It's just unfortunate that I cannot replicate the problem reliably. It happens when it wants to.

 

[Apach 031]

Yeah it's been a pain trying to find the issue. What's so weird is if I immediately disconnect and reconnect the battery, all is fine. I've been inspecting the wiring everywhere I can, repaired one section that was causing a different problem.

My codes pop on both the high-speed and low-speed networks. There is one common denominator... the VCIM (onstar) module. Both networks go through it. I may just try and find a used one to swap in and see what happens. It's just unfortunate that I cannot replicate the problem reliably. It happens when it wants to.

Can I just say, I've been watching this thread, and nice job everyone. Ive got a similar random issue that acts up every few weeks. Seeing you guys report your diagnostic process, and especially reporting back on what works and what doesn't, is just so refreshing. Too many threads for mystery ground and BCM issues with no follow up. Much appreciated, I'll keep watching!