Has anyone seen this before?
I'm struggling to troubleshoot an electronics problem on my 2004
Chevy Suburban. I've obtained the shop manuals and a diagnostic
scanner to pull the trouble codes to help but, alas ... it still
eludes me!
Here's the problem; I will be driving down the road and all is well.
Suddenly, the door locks will unlock/relock and the engine will
stumble. I'll see a couple of indicator lamps light up and the speedo
will drop and then recover. Some times the MIL will be illuminated
permanently, sometimes not. More recently the Message Center will
start scrolling messages like; "Service Stability System" and "Reduced
Engine Power". I've had to pull over sometimes as the engine
occasionally cuts out completely and won't restart. I've disconnected
and reconnected the battery on the side of the road and sometimes that
will allow me to get home. A couple of times I've called my wife and
she'll pull me home using the older, yet more dependable 1996 Suburban
(a fact she frequently reminds me of when I attempt to extol the
virtues of my 2004 Burb).
I've correlated this problem (high confidence) with striking a
pothole or bump in the road which leads me to believe I have a loose
connection or bouncing relay that powers some critical module. I've
pulled a number of DTC's from the system but the most frequent is
U0107 indicating some kind of communication loss has occured.
I have also managed to curb the problem for about a week when I moved
and reconnected some of the connectors on the BCM (located under the
steering column). I had removed and reseated the PCM connectors but
that had no effect. The TAC Module also seems to be related in that I
removed one of the connectors to the TAC (located on the Firewall on
the Driver's Side) while the engine was running but parked and the
same messages popped up on the Message Center (Service Stability
System and Reduced Engine Power). Of course the door locks didn't
reset because I wasn't moving and didn't have them locked. I suppose I
could try this experiment again with the doors locked sitting in the
driveway and see if they reset like they do when I'm driving.
I am suspicous of the BCM being involved but I can't bring myself to
simply replace it w/o troubleshooting down to root cause. I may end up
buying and having a new BCM programmed (not a cheap endeavor, $249 for
the module and another $100 to get it programmed at the dealership)
only to find I still have the same problem. Besides, there's not much
on that module which would appear vulnerable to mechanical shock.
Has anyone ever seen anything like this before? I'm open to comments
and suggestions.

Thanks,
Jack Wagner
jack_wags@verizon.net