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How to Install 4-Way Trailer Connector on 1999 Chevrolet Silverado 1500 with Factory Tow Package


Veh has factory tow package, w/wiring bungle above spare. I have a Tow Ready part # 118315 which is supposed to be specific for my veh. The T-connector adapter doesnt appear to match any of the 4 plugs underneath L rear a box with 4 separate plugs. This part terminates with 4 pin veh side connector. I also have Tow Ready part # 20109 which has the trailer end wired separatly to plug into the veh side of the previously noted Tow Ready part. I have 4 wires coming from the Tow Ready # 20109 which are: Black, Blue, Yellow and white wire has ring connecter pre wired. HOW do I connect to be functional. This should be extremely easy yet is frustrating. Please advise.


Expert Reply:

The Tow Ready T-One Wiring Harness, part # 118315, is for the 1988 to 2000 Chevrolet C/K Series trucks. It is not for the 1999 Chevrolet Silverado 1500.

The 1999 Chevrolet Silverado 1500 would use either the Tow Ready Wiring Harness, part # 118384, which is used if you have a harness that is located under the vehicle, behind the bumper, on the driver’s side of the vehicle. The wiring harness # 118384, is meant to plug in line with the factory wiring and provide a 4-Way flat connection. The 4-Way will provide left and right turn signal functions, brake light functions, and running light functions. I am including a link to the instructions on the Tow Ready harness.

The other wiring harness to use on your vehicle for a 4-Way flat connection, part # 18252, would work if you do not have the tow package. This harness will hardwire directly to the bundle of wires above your spare tire.

I would recommend to use the included tester and test the wires for function. This is how the wires should normally be attached by color.

Yellow wire on the harness will attach to the yellow wire above the spare and is for the left turn and brakes.
Green wire on the harness will attach to the Dark Green wire above the spare and is for right turn and brakes.
Brown wire on the harness will attach to the Brown wire above the spare and is for tail lights.
White wire on the harness goes to the white above the spare and is for ground.

The Tow Ready # 20109 is a 4-Way to 7-Way adapter. This will plug into the 4-Way on your vehicle and the remaining wires are:

White wire is for ground to vehicle frame.
Blue wire is for electric brakes and connects to output wire on the brake controller.
Yellow wire is for auxiliary 12 volt power, reverse lights, or reverse lockout for trailer brakes
Black wire is for 12 volt power and will connect to vehicles battery with fuse or breaker.

I hope this will help you make the correct connections. If you have any other questions I will be glad to help. I am including a link to a FAQ page on installing a brake controller and trailer wiring on Chevrolet and GMC trucks.

expert reply by:
Jeff D

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