I have a 1991 camry that the taillights quit working on. The fuse is good, the headlight switch is good, and the side marker lights work, brake lights work and turn signals work, but no taillights. What could be the problem ?

 

If you have rear side marker lights, the Tail fuse and relay are working.

Might start by checking for DC power at the bulbs. Wire might be green or light green in color. Then check the light bulb ground wires, White/Black stripe.

If ground ok but no power it could be the wiring or the light failure sensor. The light failure sensor is supposed to sense if a tail or brake light goes out. It located in the trunk, drivers wall side, behind rear tire.

Determine if power is available at the green wire.