trailer wiring

duanew1 · May 18, 2006

I have an 2005 HD 2500 and i switched over my brake control for my trailer from my 2000 Chev. I put a fuse in the underhood fuse box and wired everything up. Everything works correctly....with one problem. The brake controller ONLY works when the headlights are manually turned on. All the lights, turn signals, brake lights, etc. work just fine with or without the headlights on.... just the brake controller won't work without them. Any help or advice appreciated.

Draenor · May 18, 2006

Sounds like you wired the hot wire for the controller on the hot for the lights. When you turn the light switch to on, it sends the power to the controller.

duanew1 · May 18, 2006

All i did was use the already wired plug..... no bare wiring.

Worktruck · May 18, 2006

The wiring for the controller is different from 2000 to 05. Do a search here on the forum and you should get some answers. I believe there are just a couple ofg wires that need to be switched in the pig tail for the controller. Good Luck.

Shawn T · May 18, 2006

The wiring for the controller is different from 2000 to 05. Do a search here on the forum and you should get some answers. I believe there are just a couple ofg wires that need to be switched in the pig tail for the controller. Good Luck.

<{POST_SNAPBACK}>

Worktruck hit it on the head. In 03 they changed the pin-out on the trailer brake controller wiring harness. You have to swap two wires. When I traded my truck (99 Silv) for my current 03 I just pulled the old harness out of the old truck. Found out the hard way. I just went to the dealer had them pull an 03 harness out of the box and immediately seen the color difference on the incoming wires. Swapped the two wires, it took 30 seconds. Took my old harness with me, plugged it in, and has worked like a charm ever since.

MS3DALE · May 18, 2006

Yep,They changed the wiring for '03.

Maybe this will help a little.....

Document ID# 1644053

2003 Chevrolet Chevy K Silverado - 4WD

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Subject: Trailer Brakes Applied When Headlights/Park Lamps Are On, Brake Controller Illumination (Modify Brake Controller Wiring Harness) #02-05-22-004C - (04/05/2005)

Models: 2002-2005 Cadillac Escalade, Escalade EXT

1999-2005 Chevrolet Silverado

2000-2005 Chevrolet Suburban, Tahoe

2002-2005 Chevrolet Avalanche

1999-2005 GMC Sierra

2000-2005 GMC Yukon, Yukon XL

2003-2005 HUMMER H2

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This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 02-05-22-004B (Section 05 -- Brakes).

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Condition

Some customers may comment that when the headlamps or park lamps are on, the brakes on the trailer are always applied, or that the back lighting for the trailer brake controller only illuminates when the brakes are applied.

Cause

The cause of this condition may be due to wiring changes within the vehicle electrical system for the 2003 model year.

Correction

Inspect the brake controller wiring harness jumper that is plugged into the vehicle relay block-body. The relay block-body is located under the left side of the instrument panel near the left kick panel, behind a plastic cover.

The 1999 though early 2003 wiring harness jumper that plugs into the relay block will have a reddish/brown 6-way connector and a tag with the last four digits of the wiring harness part number. Second design 2003-05 may have a white plastic connector with part number 5418 as well.

• The 1999 jumper is/was P/N 12171982 with a pink/purple tag identifier of 1982. This number has been superseded to 15366255, with a pink/purple tag identifier of 6255.

• The 2000 jumper harness is P/N 15366255. The pink/purple tag identifier is 6255.

• The 2001-2002 jumper is P/N 15086884. The orange tag identifier is 6884.

• The 2003-05 jumper is P/N 15085418. The orange tag identifier is 5418.

When transferring the brake controller with the wiring jumper attached from a 2001-2002 vehicle to a 2003-05 vehicle, a change to the jumper harness connector must be performed.

The following information is for the 1999-2002 wiring harnesses.

Wire Color

Circuit Number

Function

A

LT BLUE

1620

Stop lamps

B

RED

142

Brake controller 12 volt source

C

DK BLUE

47

Brake Controller output (Trailer Brakes)

D

BROWN

2409

Brake controller illumination

E

--

F

BLACK

1850

Ground

The following information is for the 2003-05 wiring harness.

Wire Color

Circuit Number

Function

A

BROWN

2409

Brake controller illumination

B

RED

242

Brake controller 12 volt source

C

DK BLUE

47

Brake Controller output (Trailer Brakes)

D

LT BLUE

1620

Stop Lamps

E

--

F

BLACK

1850

Ground

To modify a 12171982, 15366255 or 15086884 harness for use in a 2003-05 vehicle, switch the wires in cavities "A" and "D".

To modify a 15085418 harness for use in a 1999-2002 vehicle (see model list at the front of this bulletin for applicable models), switch the wires in cavities "A" and "D".

Warranty Information

When the correct wiring harness P/N is matched to the specific model year of the vehicle, everything works properly. Therefore, conversion of an incorrect wiring jumper to match the vehicle would not be considered a warrantable repair.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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Document ID# 1644053

duanew1 · May 18, 2006

The wiring for the controller is different from 2000 to 05. Do a search here on the forum and you should get some answers. I believe there are just a couple ofg wires that need to be switched in the pig tail for the controller. Good Luck.

<{POST_SNAPBACK}>

thanks! I will try that......