I've found that pin 5 and 6 with the power +12 constant and on radio are not showing any power when the radio is on. Any ideas on tracing the failure to provide power from the head unit? Where is the relay that powers on the subwoofer?

 

96 thru 99 1/2 it's behind the passenger kick panel...... which is telling you your floor might have a hole or your windshield is probably leaking.