Troubleshooting 2000 GMC Sierra 1500 Wiring Functions

Updated 12/01/2014 | Published 11/29/2014

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7-Pole and 4-Pole Trailer Connector Sockets w/ Mounting Bracket and Wiring - Vehicle End

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$95.28

Hook Probe Circuit Tester

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$12.94

Question:

Hello, I followed a 2002 Chevy Silverado wiring diagram for my 2000 GMC Sierra and the passenger tail light will stay on, the driver tail light will not turn on, and the drivers side light will blink for both right and left turn signals.

asked by: Greg D

Expert Reply:

You will need to wire the Pollak 7-Pole and 4-Pole Trailer Connector Sockets, # HM40975-11998, for function rather than by color. Wiring color is not an exact science. A company may change wiring color even within the same model year. The best way to determine functions of your wires is to test them for function with a circuit tester, like part # PTW2993.

To test the wires using a circuit tester, first turn on the left blinker. Find the wire that carries a signal in unison with the blinker. This is your left turn signal wire. Next, do the same with the right blinker. Then, find the wire that has a constant signal when the lights are on. This is your running light wire. Do not confuse it with the 12-volt hot wire which will have a constant signal when the lights are off.

With the vehicle in reverse (best to have a helper in the vehicle applying the brake while it is in reverse, and engage the emergency brake) find the wire that has a constant signal. This is your reverse circuit. The last wire is for the electric brakes. If you have a brake controller installed, have someone engage the manual override on the brake controller. Then find the wire that carries a signal when the brake controller is engaged. The remaining wire is the ground.

Once you know the functions you can use the wiring configuration at right to help you wire your vehicle.

I have also included a link to trailer wiring diagrams for you to check out.

expert reply by: Chris O