how to repair a right rear signal and brake light? on 1999 Ford Expedition

Replaced the bulb, replaced the brake switch, replaced the arm for signals and cruse control. Checked the connection at the bulb that has power. Check the wire harness on passenger side up to the kick panel on passenger side. Where do I go from there. Help!!!!!!!!!!!!

Asked by for the 1999 Ford Expedition
Run a ground wire to that bulb to see if it will work then. Sounds like the ground circuit is open!