Troubleshooting Loss Of Trailer Running Light Function On A 2019 Toyota Highlander XLE

Question:

2019 Toyota Highlander XLE wi. tow package. I bought a hitch and pigtail and it had been working fine for the past three years. Now- no lights when plugging into trailer lights. I checked ground back to the battery neg- all good. No voltage at the pigtail contacts- nothing. Checked voltage at the factory four pin molex plug- nothing. Checked fuses under hood- no 30a fuse in the towing slot and the system worked without it. I added a 30a fuse there anyway- nothing. I carefully removed the tape and sheathing on the factory wiring upstream from the molex- no damage I called the dealer and ran my VIN- they confirmed that it is equipped with the tow package. Once again- the lights have worked for the past three years. Any thoughts on what to check next? BTW- the vehicle brake and turn signals work fine.

asked by: Jonathan K

Expert Reply:

Hey Johnathan,

Since you've already checked the fuses and found everything was fine that leads me to believe that the Hopkins Plug-In Simple Wiring Harness # HM11141825 has an internal short. I recommend unplugging it from the factory connector and then turn on your running lights. You can then test the factory connector using a circuit tester # PTW2992 to see if the signal is coming through. If it is then we know the # HM11141825 just needs to be replaced.

If the signal isn't coming through then you have an issue either with the factory wiring or the fuse block isn't making good enough contact with the fuse to complete the circuit.

expert reply by: Kevin C