Troubleshooting 4-Pole Trailer Wiring Harness on 2001 Dodge Grand Caravan

Question:

Recently wired a vehicle for 4 prong trailer wiring when finished noticed that the dash panel lights are not coming on or working, only half of the speedometer light worked the rest do not work not sure what happened but when I turn on the park light I hear a click when I turn it off I hear a click same way with the headlights

asked by: Kat

Expert Reply:

The 4-pole trailer wiring harnesses for your 2001 Dodge Grand Caravan, such as # 118376 and the others shown on the linked page, install with plug-on connectors at the driver's side tail light assembly as shown in the linked installation video, which shows a 2001 Dodge Grand Caravan.

The 4-pole wiring makes no connection whatsoever to the dash panel lights nor to the lights for the speedometer. These are entirely separate circuits.

Does this problem go away if you unplug the wiring harness? If so, then you could have corrosion within your connectors. Inspect the OEM wiring that connects to the taillight/harness for any signs of discoloration or corrosion that could be causing a short-circuit. Clean as needed.

Since you are hearing a 'click' sound this suggests that a relay may have gone bad on your headlight circuit, which DOES interact with the wiring harness. The brown wire for the trailer running lights does connect to the headlight circuit on the vehicle so this would be the one to focus on. Check for any blown fuses/relays for the headlight/running light circuit in the GC's power distribution box.

If everything behaves normally when the harness is completely removed then your wiring harness may be the source of the problem.

expert reply by: Adam R