Here you go, I would check the output at the four pin plug withthe trailer disconnected. If both right and left signals are working and the brake is not, the problem is in the converter box.Good luck.

 

I was able to use the diagram you put up, find the brake light wire and reseat the connector and it worked! Saved me a couple hundred dollars and it took me less than an hour. Big thanks

 

I know this is an older thread but this past week I finally got around to installing the wiring harness on our 2020 CX5. I installed the factory hitch way back when we bought it new and just never got around to the harness!

As another member posted here (sorry I forgot your username) don't bother with the, "Supplemental Trailer Hitch Harness" or the "Reroute" kit. It's just seven 14" black zip ties and the instructions that you can download electronically.

It guess the original instructions routed the harness a little too close to the exhaust and gives instructions on how to disconnect the wires final plug to where it goes through the grommet into the rear of the car and how to then a better route to keep it a bit further away.

Since I was installing the harness for the first time I had to follow the reroute directions backwards.

I'll try to attach the reroute directions here.

Good luck everyone!
Larry.