2008 Electrical Issue

[pjp]

I have a 2008 2500HD with a 6.0 automatic. A few months ago, I noticed that sometimes (about 6 times a week) the radio display would be dim during the day, but it worked normally. I first thought that the light sensor on the dash was going out, but now I've found that when the radio issue occurs the four wheel drive knob is dark and doesn't do a thing. It doesn't flash when trying to shift or activate the transfer case motor. In frustration (when I really needed 4x4), I recycled the ignition key and noticed that the radio was bright again and the lights on the 4wd knob were illuminated. I tried the switch and it worked like a champ.

 

This week I took it to the dealer and unfortunately there were no codes set or in the history. It seems like there's only one way that these two systems integrate and that's through the serial data links for the radio module and the transfer case shift module to the Body Control Module BCM. Unfortunately the dealer doesn't want to replace the BCM without a code...

 

Can you help or make a suggestion?