Communications Bus / possible BCM issues
Hi all, I'm having a problem and want to see if anyone has ideas before I just start tearing into this thing.
Car: 2007 Lumina SS (basically G8 gt with a few differences)
6.0l L76, 4 speed auto (4l60 i think, but haven't figured it out yet)
Single Zone Manual Climate control
Base radio (not touch screen)
Issue: generally when cold, but occasionally when its warmed up also, I'll get a "Stability Control Off" message in the dic, this is always accompanied by harsh shifting. It'll stay off for anywhere between 10 seconds and three minutes and then go away. Normally its on the first start after it sits a while (IF it is going to act up) and then works normal by the time I'm 2km up the road or so. It doesn't seem to be triggered by any particular event. bumps, turns, accelleration, or braking dont' seem to have an effect either way. Sometimes it'll give me the message before I can even get it out of park leaving the house, other times it does nothing the entire day.
Also related, occasionally the ac blower will stop, when it does the a/c light and the recirc lights will turn off. Moving any setting on the HVAC will bring it back online. When this happens it completely resets the climate control and the blend air and mode door actuators have to move before the desired operation is restored.
WHAT I KNOW so far:
using a tech2 emulator I have come up with the following items:
EBCM module no communication
BCM no communication
U0214 CAN-Bus No Communication with RFA (Remote Function Actuator)
U0184 CAN-Bus No Communication with Audio System IRC (Integrated Radio Chassis)
U0164 CAN-Bus No Communication with HVAC (Heating Ventilation and Cooling)
U0155 CAN-Bus No Communication with IPC (Instrument Panel Cluster)
Now the obvious answer is there is likely a communications issue somewhere that will resolve the entire set of issues I'm having. In full disclosure, its hotter than hell here and I haven't done any actual diagnostics yet outside of re-seating the ebcm connector which didn't make any difference. When Its acting up there is no communication from the scan tool to any modules on the low speed bus.
I don't have any good wiring diagrams for this car but if its like most gm cars of the era, the only place that both the low and high speed bus meet up is the body control module so that is my number one suspect currently. Is anyone aware of any common wiring splices that give issues on these cars or places where wiring gets rubbed through that may be shorting out something and causing the bcm to go offline? This weekend I'll pull the under dash panel out and check all the bcm wiring I can find and the connectors but I'm not real hopeful it'll be that easy. Do these cars have known issues with body control modules failing in weird ways like this?
I'm good at diagnostics and great with electrical, just hoping for some direction to go in before I start ripping stuff out to test. Thanks for reading this far!