Troubleshooting Trailer Brake Lights Do Not Work When Brakes Applied on 2001 GMC Yukon
Question:
I have everything hooked up to my 2001 Yukon and everything works but my brake lights. Wen I step on the brake my tailights go off with everything else.
asked by: Kevin
Expert Reply:
The first thing I would do is to use a circuit tester, like # PTW2993, to test the vehicle side trailer connector with no trailer connected. If your 2001 GMC Yukon has a factory installed 7-Way, test the pins in the 3 o'clock and 9 o'clock position. Have someone step on the brakes while testing the pins. The test light should show a signal. If it does not, then something is wrong with the wiring on the vehicle, and you will need to trace the wires back to look for any broken or loose connections.
If the functions are correct at the trailer connector, plug in the 7-Way to 4-Way adapter, if applicable, and test the pins on it. The two pins furthest from the ground pin carry the brake and turn signals. Test them with the circuit tester. If the trailer connector on the vehicle was working properly but the adapter is not, then something is wrong with the adapter and it will need to be replaced.
Finally, plug in the trailer, and test the functions on the wires directly behind the trailer side connector. If the functions are not working properly, then something is wrong with the trailer wiring. It could be a bad ground or a broken wire. Check all the grounds on the trailer, including those behind the taillights, to make sure they are attached to clean and corrosion-free locations. You can also check the wiring on the trailer to verify that it matches the functions and pin locations on the vehicle or the vehicle via the adapter using the wiring FAQ linked below.
If the trailer you are towing has a large amount of lights on it (extra marker or clearance lights), it may be too much of a draw on the electrical system. Since the brakes require more power, the additional power draw may be too much for the system, causing it to fail. I have included a link below to a wiring FAQ that might help when checking the wiring.
Products Referenced in This Question
Product Page this Question was Asked From
Adapter 7-Pole to 4-Pole and 5-Pole
- Trailer Wiring
- Wiring Adapters
- Multi-Function Adapter
- 7 Round - Blade
- Plug Only
- 4 Flat
- 5 Flat
- Hopkins
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