my in-laws have a 2008 silverado 4.8 2wd CCSB we all use as a work truck. it has about 180k miles on it now.

here are some scenarios i've personally experienced at least once.

1. when using the blinkers, the cruise sometimes disengages, and the truck jolts.

2. sometimes the glitch/jolt happens without using the blinkers. usually the lights on the cluster go crazy for half a second.

3. if you park the truck and turn it off (to go into the store or something), nothing will power up when you turn the key on...

4. when you disconnect the battery for a minute, it starts and works fine for a little while.

next time i see the truck(2 hours away), i'm scanning it with EFI live to see if there's a history code, but i'm assuming there's a bad connection somewhere causing the CAN to go haywire.

any similar experiences with GMT 900's??

 

my moms malibu, similar electrical wise, did that as well when the battery was completely dead and running off the alternator. not sure how good or bad your battery is but that might be a good place to start. also, check your grounds.