Troubleshooting Jeep Lights Not Working with Flat Tow Harness

Updated 05/17/2019 | Published 05/16/2019

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Question:

I have a 2004 Jeep LJ Wrangler. I attached the harness and when I connect to the RV, the lights are not synced with the RV. When not connected, I do have nornmal light operations for the Jeep. What am I missing that the lights don’t work when hooked up to the RV ?? Thank you for your time in this matter.

asked by: Lance

Expert Reply:

Since your Jeep lights work normally when it is not connected to your RV your harness # HM56202 is probably connected properly. I suggest you test the motorhome connector to confirm that the correct lighting signals are present there. You can use a circuit tester like # PTW2992 on the contacts while a helper activates the brake, turn and running lights on the coach. Please refer to the linked article on wiring to see which contacts handle which signals on the various types of RV connectors.

If the signals are present on the RV then move on to the harness and test the wires from the 4-pole that lead into the module to confirm signals are making it that far; then test the output side wiring of the module that carries those signals to the Jeep's lights. If signals are present before the module but not after it, then the module/harness is bad.

expert reply by: Adam R