We don't have that truck anymore, but I was having a discussion with a diesel mechanic the other day about these strange electrical issues with the '05 and '06 Chevys. He told me that most of them are caused by the BCM (body control module). If we'd known this before we got rid of it, we would definitely have tried that fix. Wish one of the other numerous mechanics we had it in to would have known to try that. Loved that truck! But the electrical issues got to be too much. We replaced both batteries 3 different times, and replaced the alternator 2 or 3 times. In the end, it would light up, the door bell would ding, everything looking like normal, but as soon as you turned the key, it would "act dead". Barely hook up jumper cables and it would fire up immediately. We would have it out on a job site, been running for better than an hour....turn it off, and 2 minutes later it would not start....playing 'possum on us. Very frustrating. Finally decided it wasn't worth it anymore, so traded it in. Now we're stuck with all the sucky government regulation BS on the newer truck.