Troubleshooting Tekonsha 7-Way Install on a 2023 Toyota Highlander Hybrid

Question:

Hi there, I’m testing a wiring harness for my 2023 Toyota Highlander hybrid limited. I bought the Tekonsha OEM Replacement Vehicle Wiring Harness # TK57VR22125. The light for the brake does not come on when brakes are pressed. However on the trailer the lights are always on as if the brakes are pressed. All other indicators work as they should. Any idea if this is a trailer or wiring harness problem?

asked by: Jon V

Expert Reply:

You could honestly have a problem on either the vehicle side or the trailer side. The best way to check is by using either a different vehicle or trailer to see if the problem duplicates. If you do not have another trailer or vehicle with a 7-way a Test Light # PTW2993 or 7-Way Tester # PK12741 can be used to verify if your vehicle wiring is correct.

Often times when you have a wiring issue like you describe it is from the tail lights being connected backwards on the trailer. You may have the brake/turn lights wired to the running lights circuit. This means the brighter filament in the bulb is getting power from the running lights making the others harder to see. You can use the Test Light # PTW2993 to test this at the lights on the trailer as well.

expert reply by: Bud M

Jon

4/3/2024

I did a terrible job explaining. I have the 7 way connector test tool. When plugged in the little red light labeled brake does not come on when brakes are pressed. All of the other little red lights work. Does this change your answer by chance? Thank you!

Bud M.

4/3/2024

@Jon Thank you for the additional information. So that light is going to be for the brake controller output. If you do not have a Brake Controller # 90195 installed then this light is not going to come on. Also some controllers are not compatible with some testers as the controller will give off a small amount of power to verify a connection and others only work when the vehicle is moving.