2002 Chevy Silverado Tow Package Turn Signal Circuits Work But Not Brake Light Circuit

Expert Reply:

I would start by testing at the trailer connector on the vehicle. The pins that carry the right and left turn signals also carry the brake light signal for each side. Use a tester like part # 40376 on the pins at the 3:00 and 9:00 positions in the connector. Both pins should show current when the truck brakes are applied. If they do not, there might be a blown fuse in the box located under the hood of the truck on the drivers side fender well.

There should be a legend on the underside of the fuse box lid which will explain which fuse protects what circuit. Pull and examine any fuses relating to the trailer lights, there are several of them. If you locate a blown fuse, make sure the trailer is unplugged and replace the fuse. You will then need to examine the trailer connector on the vehicle and the trailer wiring to locate and repair the short that caused the fuse to blow. Look for corroded or loose connections, pinched wires and cracked or worn wire insulation that would allow a wire to short to the trailer frame.

If you cannot find a blown fuse, according to my contact at Tow Ready, you probably have a bad tow package module. Rather than a costly trip to the dealer to repair this, the most expedient and cost-effective method of repairing the problem would be to install a tail light converter like part # 119190KIT, cut the 4-pole connector off the end of it, and wire it directly into the 7-way connector.

You would locate the applicable tail light circuits behind each tail light assembly, and tap each converter wire into the tail light circuit as shown in the instructions I will link you to. On the output side of the converter, the green wire would connect to the # 6 terminal on the 7-way connector, the yellow wire connects to the # 5 terminal, the brown wire connects to the # 3 terminal and the white ground wire attaches to the # 1 terminal. The vehicle tow package wires that were originally connected to the # 3,5 and 6 terminals should be disconnected and capped off.

The black power wire from the converter would be ran under the vehicle to connect to the positive battery terminal. When routing the wire from the rear of the vehicle to the front, make sure to avoid hot areas like the exhaust system and any moving suspension, steering or drive line parts.

I have linked you to an install video featuring the wiring harness I recommended. Although the video shows the harness being installed on a different vehicle, the procedure for testing the tail light circuits for function might be helpful to you.

expert reply by: Mike L