Wow I've had a time with the lighting on this truck. Most recently the running lights and the left turn/brake stopped working on the 7 pin trailer tow. Not getting power to the plug for those functions. Right turn and brake light work. I replaced the box under the steering wheel in an attempt to correct the running light issue. That didn't work. Checked all the relays and fuses seem to be in order. Any suggestions?

 

I assume you have tested power to the 7-pin connection on the truck while applying the brake and activating the turn signal. Since you replaced the trailer module (that box under the steering wheel) and still have the problem, you might want to check the following: Check the connection behind the 7-pin, ensure it is tight and no dirty contacts. If you have the jumper harness to the bed 7-pin for 5th wheel, check those connections as well. Test the 4-pin connection, is it operating correctly? Check the trailer wiring for shorts. The Body Control Module can temporarily shut down the output if excessive current is detected. Use a DTC reader to check for error codes and clear error codes to reset the BCM and enable the outputs.

 

Thanks for both replys. I've checked everything that I can access before the plug at the back of the truck. I have no power on any wires except right turn and right stop. I do not have a brake controller installed. No 5th wheel connectors only 7 pin and 4 pin.

 

You said you checked all the fuses and relays?

Battery Junction Box fuses: F27 (trailer battery charge relay), F42 (Trailer Tow Module), F54 (Trailer Brake Control Module), F65 (Trailer Tow Module), F72 (Trailer Left/Right and Stop lights), F99 (Travel Trailer Parking lamps), F84 (Travel Trailer Backup Lamps Relay)

Do you have power to the 4-pin connector?

 

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