All Trailer Lights Come On when Connected to 2017 Subaru Forester with Curt Wiring Harness

Question:

Hi. I installed c56040 on my 2017 Forester. The headlights bring all the trailer lights on, but turn signals and brake lights on the trailer dont function. The trailer lights all work fine on my 2010 Forester. Suggestions? Thanks in advance.

asked by: Sean

Expert Reply:

With the trailer disconnected from your 2017 Subaru Forester use a circuit tester such as # PTW2992 or a meter if you have one to test the 4-Way trailer wiring harness # C56040. Have someone sit in the vehicle to operate the lights. First turn the headlights on. Then test the pins on the 4-Way. If more than one pin has power, then that indicates a short inside the converter box and the whole harness will need to be replaced. I suspect that this is the issue but if not, there are other tests. I have linked a help article on testing the 4-Way and a video on testing a converter box for you.

expert reply by: Michael H