I'd start by having the battery and generator tested. If the generator is defective, especially if all it can deliver is one third of its rated current, replace the battery too. GM has a big problem with their generators. Due to their design they produce huge voltage spikes that can damage the internal diodes and voltage regulator, and they can cause the numerous computers to do weird things. The battery is the key component in dampening and absorbing those voltage spikes, and they lose their ability to do that when they get to be around two years old.
GM also had a real high failure rate with their radios. To be sure you have it fixed at one of their two grossly over-priced repair centers they cleverly built the Body Computer into it so it has to remain in the truck. If you replace it with a higher-quality aftermarket radio you will lose the functions it controls like producing the sound for the signals. They also stopped allowing us to buy their radio service manuals so the less-costly independent repair shops can't work on them for you.
Saturday, June 8th, 2013 AT 7:27 PM