my right rear turn and stop lamp do not work. The trailer harness has the same problem. I checked the connector by the spare in the frame and all looked ok!! Ideas?? 2001 f150 4x4

 

First suggestion would be to check the bulbs for blown filaments or poor contact at the socket, and the fuses - just a good practice so as not to overlook the easy stuff - although with the problem extending to the trailer harness, thinking you may end up getting a voltmeter and to start chasing voltages.

 

I agree with checking voltage. If you have power then check the ground.

 

a bad ground has usually always been the reason with any of my electrical problems in the past.