Troubleshooting Brake Light/Turn Signals not Working on a 2004 Toyota Highlander

Question:

Hello, I purchased this wiring harness for use with my 2004 Toyota Highlander and a 6 pole adapter in order to tow a recreational vehicle. My issue is that I am only getting power to my rv for the running lights. No brake lights. No turn signals. All of the electroncs on my Highlander are functioning properly. The 6 pole plug on the rv was testing with another vehicle with a native 6 pole plug and all lights worked properly: running, brake, and turn signals. Any insight on this would be much appreciated. Thank you.

asked by: James

Expert Reply:

The first thing I would check would be the Tow Ready Wiring Harness # 118413 for voltage on the turn signal and brake circuits. I attached a video that shows how this is done.

If you find that your 4-way is not functioning correctly I would go over the installation instructions I attached and make sure all of the connectors are making secure connections. You will also want to make sure the ground strap of this unit is making a good connection.

Once you have checked the connections you will want to check the the box of the # 118413 to determine if it is in correct running order. In order to do that you will need use a circuit tester # PTW2993 to check for voltage going into the box and then for voltage coming out of the box. If the correct voltage is going into the box but not coming out of the box then you know the converter is the culprit and it should be replaced.

If the problem is before the box it is either the connectors used to install into the vehicle wiring or it is the vehicle wiring. The best way to track down either problem will be to use a circuit tester and test for voltage everywhere going further and further up the wiring circuits until you eventually find the problem.

expert reply by: Jameson C