Strange electrical problem with ignition switch wire - FIXED

[e9coupe]

I had a strange problem with my '03 GMC Sierra but was able to figure it out and thought I'd post a summary in case someone else can benefit from it.  The symptoms were random and odd.  The ABS/Brake dash lights would come on every couple weeks and the chime would go off a million times, then started happening more often and finally started happening when I'd turn the key to the "on" position before starting the engine.  I figured it had something to do with the ABS module maybe and would look into it, except that when it got really bad it was at the same time my A/C blower and electric windows wouldn't work.  AND, the transmission would go into "limp mode" and stay in third gear.  I figured it had to be related since it all started going bad within one day, then the truck wouldn't start at all, luckily in front of my house.  I suspected the ignition switch since that's a place where multiple components are powered.  I grabbed a good used switch (I work at a wrecking yard) and swapped it out and that didn't help so I checked power to the switch.  One wire was hot going to the switch but when I rotated the wheel to acc and on positions only a ocuple wires lit up out of eight!  Good switch but power not being distributed.  Turns out that there's two power wires that go to the switch, in my case both red wires (some schematics show red and red/wht) and the other red wire was dead.  I checked it at the fuse box and it had power, probed the wire from the fuse box to as far as I could toward the fire wall and had power, then started at the switch and probed the wire past the big connector under the dash as far back to the firewall as I could and it was good (continuity test).  So I decided I had a bad power wire at the firewall somewhere.  In my book this is weird, I've never had something like that happen before, but the bad wire was buried in the wire loom so much that I decided to cut the wire at both ends and solder a new "patch" in.  Everything worked!  The A/C and windows have worked perfectly for three weeks and the transmission never showed a problem again.  The only disappointment has been the ABS/Brake lights lighting up once in the past three weeks.  Not sure what to think about that yet.

 

Sorry for the long explanation but I think it's all important.  Hopefully no one else ever has this problem...

 

Dan

[no HD]

Hey Dan, You did what the industry calls an "overlay". I'm glad you were able to find your problem. The big secret to running down an electrical problem is don't give up. I'm with you on the ABS, not sure what that could be yet.