Troubleshooting Running Lights Stay On After Installation of ZCI Wiring Harness on 2020 BMW X5

Updated 12/15/2025 | Published 11/22/2024

Question:

Product ZCI Circuit Protected Vehicle Wiring Harness w/ 4-Pole Flat Trailer Connector and Installation Kit Part Number: 119250KIT Installed yesterday and everything worked fine. I noticed I have constant current running thru the trailer harness. With car shut off and i plug trailer connector into my trailer harness my trailer running light are on. Testing the harness I have a constant current, Is their a fix for this. 2020 BMW x5

asked by: Dave B

Expert Reply:

Hi Dave; there are a few things that may cause this issue following your # 119250KIT installation. The first is residual power that is keeping your lights on for a short while after the vehicle is off, especially if you have LED lights on the trailer. I would give it a few hours and see if the power has dissipated and the lights shut off. If they shut off after a while I wouldn't worry about it going forward.

If they stay on for a prolonged period of time it could be the ground or the orientation of the sensor. Make sure your ground is nice and secure on a clean, bare-metal surface. After that, pull the fuse to cut off power and then check the running light sensor. If it wasn't installed in the correct orientation go ahead and reverse it and that should install the problem.

expert reply by: Robin H

Robin H.

12/15/2025

Hey Dave, did the power through your ZCI wiring harness settle down after a few hours or did you end up adjusting the ground or sensor orientation? Knowing what fixed it could really help others running the same setup on their BMW.