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