Trailer Turn Signals and Brake Lights Do Not Work But Trailer Connector on Toyota Tundra Works

Question:

I was looking at an earlier thread and couldnt get an answer from that. I am using a 2000 Tundra to pull my 7 x 16 trailer w/brakes. I just now realized that I have no brake or signals. Running lights work as well as the trailer breaks. All lights work on the Tundra with or without the trailer connected. I have searched my owners manual for any information on a fuse of some kind that might be blown. There is nothing! I have read through other threads saying there is a O2 Fuse connected to the drivers side fender wall. There is no such thing on my truck. With a tester I am getting signal to the plug under my bumper. All wires are connected inside the trailer plug. I have checked all ground wires and connections to the trailer lights themselves and everything is secure. This trailer is less than a year old. The only thing I have not tried is finding someone with the same connector I have and hooking up my trailer.

asked by: Jason

Expert Reply:

Since the brake light and turn signal functions are working on the truck side trailer connector, that indicates a problem on the trailer side. The first thing you are going to want to check is the trailer side connector. Make sure that it is clean and free of corrosion inside and out. Then make sure that the main trailer connector ground is attached to a clean and corrosion free bare metal surface.

Next you will want to make sure that the grounds for the lights are also attached to clean and corrosion free bare metal surfaces. It sounds like you have already checked the wiring but if you do notice any breaks in the wiring then repair them as needed.

If the trailer has an aluminum frame, tilt bed, or folding tongue then running jumper ground wires from the lights to the main trailer connector ground can help. Similarly if you recently added a plastic license plate holder in between a light and the frame that can also interrupt the ground and a jumper wire can help there too.

You can check to see if power is getting to the lights and if it is then the issue is going to be either internal to the light or a ground issue causing an incomplete circuit.

expert reply by: Michael H

Michael W.

5/23/2020

On my seven pin connector the left turn signal works but not the left brake light. Any ideas on what to check. Thanks

Chris R.

5/26/2020

The turn and stop light circuits should be combined on the 7-Way, so I wonder if there's an issue with the converter. If you can locate the converter box, test the wiring just before it to see if you get power with both the brake and turn signal. Then test the wiring right after - if you lose the brake light signal there then the converter is bad and needs to be replaced. Let me know what you find and we can go from there.