Trailer Brake Lights Not Working After Wiring on a 2012 Toyota Tacoma Troubleshooting Steps  

Question:

Expert Reply:

I know that's frustrating, especially when you've already gone through the work of wiring everything up and all the other light functions are working. Since you mentioned that the running lights and turn signals work, but the trailer brake lights do not, I would start at the trailer connector and work your way back.

First, use a circuit tester part # PTW2992 on the brake light pin at the Tacoma's trailer connector while someone presses the brake pedal. If you don't get power there, the issue is on the truck side and could be related to a fuse or the trailer wiring harness. If you do get power at the connector, then we know the truck is sending the signal correctly.

Next, double check the brake light wire connection you made at the trailer. Since you just wired the lights, it's possible the brake light wire is connected to the wrong circuit or has a loose connection. After that, verify the trailer ground is attached to clean, bare metal. A poor ground can cause some light functions to work while others don't.

If those all check out, test for power at the brake light input wire on each trailer light assembly while the brake pedal is pressed. That will tell you whether the issue is in the wiring leading to the lights or within the light assemblies themselves.

Can you tell me if your Tacoma has a 4 way or 7 way trailer connector, and are the trailer lights incandescent bulbs or LED lights? That will help narrow things down even further.

expert reply by: Heather A

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