Radio wiring diagrams please?

I removed the third party amps (recently purchased truck in April this year) because it was causing a battery drain. I put all of the speaker wiring back to factory as the previous owners spliced in new wiring to bypass the factory amp. To simplify wiring, I installed an iDataLink harness to utilize the factory amp and to use the same head unit that was installed earlier JVC double din) in addition to use the controls on the steering wheel. I am not getting any sound, however I cannot tell if the rear amp is working correctly as it was bypassed by the previous owner. I can tell it is getting power as its heating up when the radio is on. Is there a way to test the rear amp to see if it is working correctly?