Originally Posted by jdstrickland

The obvious thing is a burnt out bulb.

The first rule of electricity, be sure the bulbs are good. Take the known-good bulb and move it to the spot where the bulb does not work.

Keep in mind that the bulbs fit into holders that then screw into sockets on the tail lamp housing. You MUST put the right bulb into the right holder, and the right holder into the right socket on the housing -- where right means correct, not the opposite of left.