'04 Avalanche Starter Issue

[2003VAAV]

Rig yourself up a jumper wire to connect battery positive to the starter solenoid where the purple wire is connected.
When the problem happens again, hook up the jumper wire and see if the starter will now crank.
If the starter now works, you know that there is an issue with the cranking circuit.
If not, the starter could be defective or there are bad power/ground connections to it.
Otherwise, it could be the ignition switch. You could then hook up a grounded test light to the starter solenoid where the purple wire connects, and then attempt to start. If the test light lights, the starter worked with the jumper wire, but you still can't crank with the key - you have a current flow issue and the problem could be the ignition switch. Many times the ignition switch has failed in GMT800 trucks. Further testing would be required. You could then bring power directly to the purple wire at the ignition switch and see if you have cranking. That might help you narrow things down some. Electrical can be a real pain. I have had a "Security" light staring me in the face since 2016!

CarMech1969

CarMech1969, you took the words right out of my mouth (I just sat down to post the same advice), I guess it's true that great minds think alike

 

[BAS-Sr]

Hmm. Just thinking aloud, maybe something related to the security system? Do you notice if the security light is on or flashes? Maybe ignition switch? Have you tried sitting in truck, take key out, lock with fob, unlock with fob then try again?

Thanks, but we have locked/unlocked the doors and there is nothing on the dash about the security.

Nice try but nope....