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Ford F-250 & Ford F-350The heavier duty full sized trucks from Ford, offering bigger, more powerful engines and drivetrains for the abuse they may go through in the workplace.
Okay so if you have verified all fuses, lightbulbs, and wiring and they all test good but you still have no running lights here is what I did.
1) Remove positive lead from drivers side battery.
2) Remove dash trim panel over fuse box if not already done.
3) Unbolt fuse box (CJB) 4 10mm bolts.
4) Locate black and grey harness on right side of the back. Pictures of what you are looking for below.
5) Locate brown wire in each, will be in the top row close to middle.
6) To test internal relay put a jumper wire across these while plugged in and turn light switch to auto or on position with the key on.
7) If you have running lights now you have confirmed that the relay is bad and you can purchase a replacement CJB or remove those wires from the harness and place them on an external relay.
I have similar issue but the jumper didn’t turn the lights on. What does that mean?
Similar issue
