I have a 2003 GMC Sonoma SL that I installed an.

Try the original radio and check the fuses first. Starting with some 2002 models, GM cleverly built the Body Computer into the radios so they could not be replaced. They had to be repaired by one of their two grossly over-priced repair centers. If this applies to your truck, look for a "radio relocation" kit. That will allow you to mount the original radio somewhere else so you still have the functions it provides, then you cut the speaker wires and run them to the new radio.