I have a 2004 chevy silverado 5.3 liter vortec engine, Vehicle will not crank. Had starter and battery checked out both were good. no blown fuses, all lights and keyless entry work radio works also. I had the PCM replaced about 3 weeks ago the Chevrolet dealer replaced the PCM they determined it was faulty due to check engine lite continuing to come on. after the PCM was replaced vehicle ran fine left it sit for 4 days and that is when this new problem started. Has it got something to do with the PCM what i have been able to find out so far is that everything is pointing towards the PCM.
It's possible that the starter relay, starter solenoid or starter motor could be bad.
If you have a test light; check voltage at the purple wire on the starter when you turn the key to the start position. If you don't; back track to the starter relay and see if you have power going to the relay.
Check fuses IGN A 40 AMP, IGN E 10 AMP in the under hood fuse box, the crank fuse 10 AMP in the under hood fuse box. The crank fuse circuit supplies power to the PCM from the ignition switch.
It is possible that the PCM could be faulty, check these suggestions first and get back to me when you can.