Troubleshooting No Trailer Turn/Stop Lights When Connected to 2018 Jeep JL Wrangler

Updated 04/13/2020 | Published 04/10/2020

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Question:

I have a 18’ JL. I recently bought a trailer to haul a kayak. The JL came with a tow package installed by dealer. I have no brake lights or turn signals on trailer. Upon looking at my fuse box f107 and f109 for left/right stop/turn. They do not have the female part of fuse to hold the 20 amp yellow micro it calls for. thoughts?

asked by: Jb

Expert Reply:

Since there are no pins for where the F107 and F109 fuses would install it makes me wonder if maybe a dealer installed an aftermarket wiring harness like the Curt # C56407 which doesn't require those fuses to operate. This kind of wiring kit tees in behind the tail lights and then draws power for the trailer lights directly from the battery on your 2018 Jeep JL Wrangler.

With that being said, since you said you don't have those lights working on your trailer the first thing to do is to determine which side of the towing rig the problem is on. Use a circuit tester # PTW2992 and check the pins on your Jeep connector. I have attached photos of both a 4-Way and a 7-Way so that you can see which pins should carry which functions.

If you don't get any signals when you activate those circuits on your Wrangler then the problem is definitely on your vehicle side and you'll need to trace the wiring on the vehicle to see where it connects. If you literally just bought the Jeep then it might be worth taking it back to the dealer to see if they'd be willing to fix it since you bought it expecting the lighting to work.

If you do get signals then the issue is on your trailer side and you need to check all of your wiring connections to make sure they are secure and not damaged, and then look at your grounds to make sure they are securely connected to a clean, bare-metal surface.

Attached is an installation video of the Curt harness if are curious as to whether you have an aftermarket kit or not, as well as a troubleshooting article on trailer lighting circuits that you can reference.

expert reply by: Jon G