I had this same problem a few months ago and thought it might have been my light bar. One of them was broken and exposed. I replaced them with LEDs and hadn't had the problem for 6-8 months. Until this week. We've had tons of rain here and the truck just completely shut down. It would restart but then would shut down again. When it dries out, it's fine. I'm thinking it's a fuel sending unit that has an exposed wire or something, that when it gets wet, it shorts it out and will not send fuel. BTW I have a 6.5L turbo diesel. Any ideas?

 

What is 'it' in your sentences? Is it the engine that shuts down? One circuit of electricity that shuts down? Or something else?

 

The whole truck shuts down, no engine, no PS, no electrical. I can stop it, put it in park and restart it, but it just dies again and will not operate until it dries out.

 

Perhaps you need an electrician to find this out? Personally under such conditions I would have had taken it all apart and put it back together, I bet you would find out why in the process even though it will take a couple of weeks for most people to do so.

 

UPDATE: Replaced the injection control module. Seemed fine Friday. Ran it through the car wash and it didn't die. Then this morning, I ran it through the car wash and it died inside the tunnel. #%&$!!!! Had to let it sit in the parking lot for 45 minutes to dry out.

 

UPDATE: I've been researching, and David at Hummer Parts Guy suggested it might be the crankcase position sensor. After reading about it, it sounds like it could be the culprit. I'll let you know after I replace/repair it.