Getting Trailer Running Lights to Work on a 2005 BMW X5 Trailer Wiring Harness

Updated 07/23/2013 | Published 07/20/2013

Products Featured in This Question

Curt Trailer Hitch Receiver - Custom Fit - Class III - 2"

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$299.65

Hook Probe Circuit Tester

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$12.41

Question:

HOW DO I HOOK UP THE NIGHT TIME TAIL LIGHTS WITH A CURT WIRING HARNESS FOR A 2005 BMW X5 TRAILER HITCH? WE HAVE TURN SIGNALS AND BRAKE LIGHTS FUNCTIONAL AT THIS POINT

asked by: James

Expert Reply:

Getting the running lights to work would require attaching the correct wire on the trailer wiring harness you are using to the correct wire on the 2005 BMW X5. It will be very similar to the video I have linked showing a typical installation of wiring harness # 119250KIT.

You will need to either use the included circuit tester with the wiring harness or # PTW2993 if you need one. Then test the taillight wiring to find the correct wire for the running light circuit. If you do have power at the 4-Way on the running like circuit but not on the trailer the issue is most likely a bad ground. Make sure the main trailer connector ground and all the grounds for the lights are attached to clean and corrosion free bare metal surfaces. Also make sure that the vehicle and trailer side connectors are free of dirt and corrosion.

expert reply by: Michael H