Troubleshooting Running Light Circuit Not Functioning on a 2003 Dodge Ram Trailer Wiring

Question:

Dodge Ram 1500 2003 Question no.1: It has a 4 pole flat female connector at rear for trailer lighting hookup. All lights brake, signal left and right are working EXCEPT the running light. Whats wrong? Question no.2: Would the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector of etrailer fix it? Please let me know so I can put in an order. Thanks for your help.

asked by: Dc

Expert Reply:

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue.

Make sure that the trailer side connector are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well.

If the wiring on your vehicle is bad you could just go with the part # C55504 to bypass the factory wiring and have a new 4-way connector.

expert reply by: Jameson C