BCM Trouble? Electrical issues.

[zachmckinney98]

Need help figuring out if it’s my BCM fried or what after welding on frame.

Truck worked fine before welding.
After, I put the battery cables back on the truck now only has a flashing dash cluster and flashing shifting knob lights.
Literally nothing else works besides headlights and door lock button on the door. Key fob doesn’t work.

Tested all fuses and relays, including the in line fuse and fuses on the battery cable. Everything is good. Good voltage.
Jumped power straight to starter fuse and engine turns over strong. So not battery.

Left unhooked from the battery over night. Still nothing. Just flashing.
Left battery hooked up overnight. Same thing.

Any ideas of what I messed up?

Thanks.

 

[SitKneelBend]

Need help figuring out if it’s my BCM fried or what after welding on frame.

Truck worked fine before welding.
After, I put the battery cables back on the truck now only has a flashing dash cluster and flashing shifting knob lights.
Literally nothing else works besides headlights and door lock button on the door. Key fob doesn’t work.

Tested all fuses and relays, including the in line fuse and fuses on the battery cable. Everything is good. Good voltage.
Jumped power straight to starter fuse and engine turns over strong. So not battery.

Left unhooked from the battery over night. Still nothing. Just flashing.
Left battery hooked up overnight. Same thing.

Any ideas of what I messed up?

Thanks.

Have you tested the battery itself? A battery on the way out can cause all sorts of strange electrical problems on these trucks

 

[zachmckinney98]

It’s reading good voltage and can turn the starter over easy.

Just tried unplugging the trailer brake module and now everything in the cab lights up but all trouble lights are lit up.
Still can’t get communication with code reader
Also, still won’t turn over with key.

Thanks.

 

[zachmckinney98]

It’s back Alive.

My PCM connectors are not in the best shape.

But still somehow the trailer brake module was causing everything.
Nothing works with it plugged in.

Thanks for the help.

 

[SitKneelBend]

It’s back Alive.

My PCM connectors are not in the best shape.

But still somehow the trailer brake module was causing everything.
Nothing works with it plugged in.

Thanks for the help.

Read codes...if there's a short on the CANBUS somewhere you will see a bunch of "lost communication with XXXX module"...that could cause this issue too.

 

[zachmckinney98]

Just saw your reply and still having issues. truck cranks up runs great but lots of codes and won't switch out of park.
And yes, I have alot of lost communication codes. Also, ABS, service electronic braking, and service throttle on dash lights.
How can I test the BUS?
And still, I'm very confused why the truck only has power when I unplug the trailer brake module. Any else seen that before?

Thanks.

 

[HarryS]

IT's on the CANbus. If it's killing the comm on the canbus, then there will be lots of failures.

 

[SitKneelBend]

IT's on the CANbus. If it's killing the comm on the canbus, then there will be lots of failures.

This^^^, and considering it corrects with the trailer brake unplugged I'd start looking there. A quick test, make note of all codes, clear them and drive for a day or so to see if all returns to normal (it can take several power cycles/hours for codes to reappear if the issue is still present or for some CELs to clear themselves). If it's all good (no new codes), you can plug the trailer brake controller back in and you will likely have immediate problems. If so, it could be something as simple as the pinout being wrong on the part and/or harness the part connects to, or a short somewhere internally (bad part) or the harness itself.

Edit: What made you unplug the trailer brake module to being with?

 

[zachmckinney98]

Sorry for late response again.
So with trailer brake module unplugged I still can't drive. Won't switch out of park. And as to how I figured it out, I was just trying process of elimination.
And codes will not clear. Tried multiple times. Probably about to take it to shop and have them hook a computer to it. All I have is the diablo tuner with code reader.
And yes, I've changed back to stock and re tuned a few times. No change.