Another Electrical issue-2001 Bonn SE

[xrayshawn]

I have a friend with an 01 Bonny SE. The car has 68K on it and is garaged (cream puff). The car has an electrical issue that I would consider minor but after searching multiple forums the "data-buss" scheme has me puzzled. Symptoms: No power windows, Locks, interior lights, keyless entry,cig lighter- I wound think simply replacing a fuse in the "fuse block" would cure it.--NOT-- From what Ive read there is a maxi-fuse box&relay center under the hood, a traditional fuse block in the dash, plus a secondary battery-micro relay block under the rear seat. My freind has spent hours checking every fuse in the car with a volt meter and they are OK. I am trying to diagnose this problem for him without looking at the vehicle-he thinks it is a multiple thousand dollar fix- and I think a simple ground or module replacement will solve the issue. By The way-does anyone know why such a complicated wiring system is justified? I have a 1999 Caddillac Escalade that soaks up 200 Amps on a hot day (160000mi, 4 heated seats, dual ac's, trailer brakes, ent system, etc) easy using the original Alternator and traditional wiring. Anyway-given the fact that all the bonneville issues are isolated to power accessories- can anyone narrow it down?