How to Troubleshoot Trailer Wiring Issues, on a 2020 jeep JL

Question:

Hi. Got this new jeep last month and installed the Teknosha kit. Super easy, brake lights, turn indicator all work, but no running lights. Seem like all in order..what should I do?

asked by: John N

Expert Reply:

There are a few ways to troubleshoot this issue. The first one would be to check your owners manual for the fuse diagram. The should be one listed for the running lights. If that fuse is good, there should also be a listing for the fuses related to towing. There are times these are not all installed from the manufacturer or dealership and just simply needs to be installed. The inline fuse that comes with # 118786 should also be checked.

If all fuses are in place and not blown, there may be an issue with the harness. One of the most common issues with wiring harnesses is the ground not being seated all the way. Make sure it is contacting bare metal with no paint or anything interfering with the contact. If that is seated nicely, the 4-Flat ports will need to be tested. The best way to check is to test all the ports on the end of the harness with a tester, like part # PTW2993. If one or more of the ports have no power, the harness will need to be replaced.

If all the ports have power, there is most likely an issue on the trailer somewhere. Using the same tester, test the wires just behind the 4 Flat on the trailer. Plugs do get worn out and can lose connectivity that way. If there is power, the wires will need to be followed as there is most likely a break somewhere down the line. It also never hurts to check the ground on the trailer as well.

expert reply by: Lazer S