I have a 90 toyota pickup with power everything and recently my power door and windows stopped working. My buddy has the same pickup with everything working and I took off his power door relay box and his master switch and plugged into my pickup and still no power. The power mirrors work just fine on both sides. But neither the passenger or drivers side locks and windows work. Any information about this subject would be really helpful thanks a lot.

 

Look for all the ground points, most are near the door just up out of site behind the dash on the cross member nuts , Loose them and retighten for starters.
Sometimes there at the bottom of the inside kick panel under the carpet.

 

Check the power source for the windows and door locks.

Get system voltage to the master switch and check from there.

One problem can be the wires from the master switch breaking where they go from the door to the cab.

Time to break out the Multimeter

Good to have the schematics of what your working on real frustrating without.