06 2500HD 6.0 is the ECM on the way out??

Tucker · May 12, 2019

I have a 06 2500HD 4x4 with the 6.0 170K miles. For the last week sometimes when you go to cut the engine off, I turn the key off and the truck keeps running. Cycle the key a couple of times and it will quit. Figured the key switch was going bad. But here's the kicker yesterday I start it up the 4x4 light flashes on and off for about 5 miles I make a stop. Get back in start the truck it is running rough cut it back off after several key cycles. Start it back up it runs fine but the 4x4 light still flashes off and on and now it won't shift out of first gear.

Drive five miles back home in first gear 4x4 light flashing maybe once every couple minutes. Get home and have to finally pull the fuel pump relay to get it cut off, because it won't cutoff with the key.

Thought the key switch was bad but now I don't know with the truck not shifting out of first gear and the 4x4 light flashing off and on??? Engine runs fine no reduced power.

Never seen this before on any vehicle and I have driving almost fifty years. Idea's where to start??? Thanks

davester · May 12, 2019

I would first go for reading codes from all the computers on your truck, to see what they've noticed, in particular the bcm (so you need something like a tech ii or autogenuity w gm enhancement).

It could be a computer problem, but it's fairly unusual. I would first consider a power/ground/wiring problem.

Tucker · May 13, 2019

Thanks, I am taking it to a shop on Monday that friend recommended to me. He is a retired tech. He mentioned it could be a ground problem as well.

Tucker · May 24, 2019

OK so update on the truck. They found a rodent nest under the fuse box on the driver side front wheel housing. They had chewed on the wiring going to the fuse panel and the chewed up wires where touching each other. The fuse panel was shorted out from rodent pee.

New fuse panel and a bunch of replaced wiring and all is good.