We recently obtained a 91 Nissan Maxima, and the (Bose)radio was not working. We bought a Pioneer cd player deck and hooked it up ourselves.
We put the interface and connection kits that Best Buy reccommended. Everything worked fine except the rear speakers weren't working. We bought Pioneer 4 way speakers to replace the Bose speakers with amps that were from factory. We found that we didn't need the interface for the new speakers in the rear and while we were disconnecting the interface wiring, we lost power to the radio, the step lights in the doors, the trunk room light and the glove box light. The 20 amp fuse in the fuse block was blown and we replaced it , but still had no power to these things.
We tested the wiring with a multimeter and found that the ignition wire works , but the battery wire has no power. Is there a circuit breaker that we are missing or is it the relay? Nissan dealer here was very unhelpful and the schematics we have don't seem very plain. Please help us to figure out how to get the power back.

 

you probably blew a fusble link.
look underhood for one that is blown

 

I checked the fusible link's under hood and in box next to battery and looks ok. Is there a relay or a fusible link some where else?
Is there a web site that has schematics on 91 Maxima? My manual does not show where step lamps and trunck lamp are wired into.

 

you need an FSM.