No Running Lights After Trailer Wiring Harness Install On a 2017 BMW X3

Question:

Hello I ordered and installed the trailer harness for my 2017 x3 BMW. I used the checker to make sure me connections are correct they are. When I connected it to the trailer, the center light and side markers dont come on. Turn signals and brake lights work fine on the trailer. I listen to your video thinking it could be a bad ground?The side makers seem to be led, black and a white wire. I will look for a bad ground, but if that was the case wouldnt I have problems with the directional and brake lights as well? This is not the case. have you ever run across this? I can send pics if needed. Thanks

asked by: Michael

Expert Reply:

I didn't catch what trailer wiring harness you were using on your 2017 BMW X3 but regardless, you will need to test the running light pin on the 4-way to see if you have power. If you do then the issue is on the trailer but if not then the issue is on the vehicle. In regards to a poor ground, this can cause all sorts of weird issues so it could very well cause a problem for the running light circuit but not the stop/turn circuits. Therefore, I would check this on both the vehicle side connector and trailer side connector.

If it turns out that you don't have power on the vehicle side 4-way for the running light circuit then most likely you don't have the correct wire attached. If it turns out that you do have power on the vehicle side 4-way for the running light circuit then most likely you have a short on the this wire between the trailer connector and point where the running light wires all splice into one another.

expert reply by: Conner L