Troubleshooting 2003 Toyota Tundra Trailer Brake Light Always On Hot
Published 11/16/2017
Products Featured in This Question
Question:
I forgot to tell you that the lights are on even if the truck is off. No other lights of any kind are on. The running lights on the truck are not on. Two places have said it is factory. So in other words. I would have to unplug the trailer evertime I’m not driving.
asked by: Brooks
Expert Reply:
The prong next to the ground on a 4-way flat is for trailer running lights. It should give you a light anytime your vehicle is running for trailer running/parking lights. If it is activating your brake light, then there most likely is a wiring issue and that can be on your vehicle or your trailer. Since there is not a factory 4-way available for your truck model year, we know there isn't a relay issue.
The brown wire is your running/park/tail lights. The yellow wire is the left side brake and turn signal. The green wire is your brake and right turn signal. The white is your ground wire.
You can test these functions using a circuit tester like # PTW2993. If you determine the issue is on your vehicle side, it is very likely that you have an improper splicing or a bad converter box. You can use the 4 Pole Harness and Hardwire Kit - Includes Tester # C59496 if your splicing is correct when tested and yet your harness is not accurate.
Product Page this Question was Asked From
Featured Help Information
Miscellaneous Media
Continue Researching
- Q&A: Trailer Running Lights Do Not Work but Brake Lights and Turn Signals Do Work
- Article: Trailer Wiring Diagrams
- Q&A: How to Test Brake Controller without Trailer Connected
- Q&A: Recommended Bike Rack and Dual Hitch Adapter for Carrying E-Bikes While Flat Towing
- Q&A: Recommended Flat Tow Setup for a 2026 Ford Maverick
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Q&A: Trailer Turn Signals Both Blink when Just Left Turn Signal is Activated
- Article: Brake Controller Installation: Starting from Scratch
- Article: Installing an Electric Brake Controller on 2007-2013 GM Full-Size Truck or 2007-Present GM SUV
- Article: Brake Controller Installation for 2007 (New Body Style) - 2013 GMC Sierra and Chevy Silverado
- Q&A: Troubleshooting Right Side Trailer Lights Not Working, Left Side Working Correctly
- Article: Troubleshooting 4 and 5-Way Wiring Installations
- Q&A: How to Activate 12V Trailer Power Circuit on 2017 Ford F-350 Super Duty
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
Brooks
11/16/2017
I forgot to tell you that the lights are on even if the truck is off. No other lights of any kind are on. The running lights on the truck are not on. Two places have said it is factory. So in other words. I would have to unplug the trailer evertime I’m not driving.