I have a 2003 F150 4X4 and the rear lights have stopped working (both parking and brake lights). I have changed the bulbs and inspected all the fuses, swapped the relays around (and the problem has not moved), inspected the wires in the steering column, the brake switch (I am assuming it is working since it will shut off my cruise control - need a schematic to completely verify) and inspected the "T" connection on the frame rail along with sanding the ground wire located on the frame rail. Nothing is working. The really strange part is sometimes the right brake light will go on and then just fade out. When I turn on the turn signal on it blinks really fast showing a bulb out (front bulbs are working). I have a factory installed trailer harness and they are working correctly. I have not tested the "T" connection with a multimeter because I can not find a good schematic for my truck. Any suggestions would be appreciated.

 

Does the CHMSL ( Center High Mount Stop lamp ) work ?

No sure why you were swapping relay, have you tried moving the tilt all the way up and testing again ?

Sometimes the connector at the base of the steering wheel pulls apart, and this causes a problem.