Troubleshooting Trailer Lights Staying On All The Time with 2019 Toyota Highlander

Updated 05/07/2019 | Published 05/06/2019

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(1139)

$45.90

Hook Probe Circuit Tester

(66)

$12.94

Question:

2019 Highlander, parking lights on trailer say on all the time. All other functions work normally, turn, brake lights, etc. With ignition/accessories off, the tail lights are always on. It is not the trailer, I used a 4 way flat trailer wiring tester with the same results.

asked by: Sean K

Expert Reply:

Since you have ruled out the wiring on your trailer as being the issue there has to be some kind of short with the wiring or converter on your Highlander that's causing constant power to be sent back to the trailer running lights circuit.

I first recommend just giving the 4-Way itself a visual inspection on the Highlander. Check for any corrosion or debris that needs to be cleaned out even though this is unlikely on a newer vehicle like yours. Then check the brown wire from the back of the connector, which would be for the running lights, to make sure it isn't pinched or damaged in any way.

If everything looks good there, then it could be a bad converter. If your Highlander has the factory tow package, then the trailer wiring converter is under the dash but if not then it would be included with the aftermarket 4-Way harness you used. In either case to test the converter you will want to use a circuit tester like # PTW2993 to test wiring going into the converter to see if you have power only when the running lights are active. If it tests correctly then test the wiring coming out of the converter. If you have power only when the running lights are on, then the issue is with the wiring between there and the 4-Way, and it will need to be tracked down.

If you had power after the converter both with the running lights on and with them off then the converter is bad and will need to be replaced.

If you still aren't able to find and resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R