pmckinley

Hi, I have an annoying fault with my 2001 xsara 1600 estate, the rear number plate lamps dont work. The fuse (f12) is fine, and anway the two sidelights (rear left and front right) which it also feeds are hunky dory. There is no voltage at the connector for either lamp. Anybody any suggestions where would be a good place to look? I've had all the trim off the rear but there are no connector joint in the wiring that i can find. i guess i shoud buy a wiring diagram.