My thought as well. I believe the P Bass deluxe has passive pickups, and an active/passive preamp. It doesn't have active pickups. If it makes sound in one preamp mode and not the other first step should be replace the battery and try both modes again.
W&T, Carvin, Elrick, and Fender Jazz basses
Bongo #54, Carvin #80, Fretless #295, Elrick #40