Toyota Repair: License plate light problem, marker lamps, electrical schematics

Question
Hello Ted,

I hope you'll be able to help me with my problem, I have a 92 corolla 4-door sedan, with the 1.6L engine.  It's in good shape and I try to do as much on it myself as i'm a student.  I'm canadian and having moved from Ontario to Québec i've had to fix some things for the safety inspection in order to change my plates.  One of these was the license plate lights not working, and i've changed the bulbs with no effect.  I haven't yet checked the fuses (doing that this morning) but I don't think this is the problem since the tail light are on the same fuse and these work fine.  So...any thoughts on what my problem could be?  I've looked at the electrical schematics in my Haynes manual but I haven't done much electrical work before so deciphering them isn't easy.  Any help you could offer would be appreciated.

Cheers,
Michel Molgat  

Answer
The tail lights, lic plate lights and side marker lamps do indeed share the same circuit but there are some connectors that could be the problem, the first thing I need you to do is to check the bulb socket for the lic plate light, remove the bulbs and check to see if there is 12 volts on the contact that has the green wire(use a test light) the other wire is white and black and is the ground wire, let me know if there is 12v at that contact in the socket, if there is voltage then there is a problem in the ground side.