Trailer Lights Work on One Trailer but Not on Three Other Trailers Towed by 1998 Toyota Tacoma

Question:

Hi, I was wondering if you could help me? I have an suv that I added a towing package two. Now here is the problem I can connect to one trailer and all of the lights work properly but on 3 others when I connect and turn the tail lights on the brake lights come on the suv and no trailer lights at all but with the tail lights off I turn a blinker on and it makes the 4 way flashers come on. Now with all of my other tow vehicles all these trailers work properly.

asked by: Jeremy

Expert Reply:

It sounds like a problem with the ground or wiring on the trailers, but it would be wise to check all of the components in your wiring system.

You can test the trailer connectors on the 1998 Toyota Tacoma and the trailers with a circuit tester like part # PTW2993. I am including a link to a FAQ page on trailer wiring that will show you the functions of each pin on your connector, depending on if it is either a 4-Way, 5-Way, 6-Way, or 7-Way. This will help you determine if there is a problem with the wiring on the vehicle or the trailers.

Also, I would recommend testing the ground connections on the vehicle and the trailers. When you find that some of the lighting functions work, but not all of them it is always best to check the ground connections.

I would check the ground on the connector on your Tacoma to make sure it is attached to a good, clean ground on the vehicle frame. Also, check the ground on the trailer connectors which should be attached to a good, clean ground on the frame of the trailers.

If all of the functions at the connectors are correct, we can turn our attention to the trailers. Start by checking all of the light bulbs on each trailer to be sure they are installed properly and in good working condition. Next, check the ground connections on each trailer light. The taillights are suspect for ground problems especially if they are grounded through their mounting bolts. A plastic license plate holder could be an issue also. If the mounting brackets for any of the lights are bolted to the trailer frame, the ground connection can be lost there also.

If all the ground connections are solid, look for a broken pinched or frayed wire that is making contact with the trailer frame or another wire in the harness.

I am including a link to a video on troubleshooting a trailer wiring harness.