So today the truck would not shift out of park; the interlock device in the shifter has failed. Upon disassembly, the solenoid that activates the device appeared to be working correctly when connected to a power source. This means that for some reason, there is no longer power being sent to the solenoid when it is supposed to. All other aspects appear to be working correctly. I removed the solenoid and tied the interlock mechanism with a piece of wire to bypass it. The truck now drives, but can be put in gear without the brakes being pressed as a result.

It would be better if Chevrolet & GM built higher quality vehicles.