trailer brake wiring

duanew1 · May 13, 2005

I have a 2005 2500 HD LS, and wired up the trailer hitch to pull my trailer. When connected the trailer brake control light comes on but it will only work when i manually move the control lever, and will only work in conjunction with depressing the brake pedal when the truck's headlights are on? weird? any help?

GM-Tech · May 14, 2005

I have a 2005 2500 HD LS, and wired up the trailer hitch to pull my trailer. When connected the trailer brake control light comes on but it will only work when i manually move the control lever, and will only work in conjunction with depressing the brake pedal when the truck's headlights are on? weird? any help?

<{POST_SNAPBACK}>

Yeah, weird, but I think there's actually a service bulletin on this issue, or something like it. I'll look when I get into work today.

c4racer · February 16, 2008

Wow - lucky I happen to see this thread. I just picked up a 2001 Suburban and found a harness on Ebay. I thought they were all compatible. Turns out the harness I got was the 5418 from 03-05. So looks like I need to swap the brown and lt blue wires to make it compatible with my truck. Good to know!! I plan to install it soon as I need to tow the race car to a shop for some work in the next few weeks.

GM-Tech · May 14, 2005

This is the TSB I was thinking of, but it doesn't sound like it fits what you're talking about...

------------------------------

Trailer Brakes Applied When Headlights/Park Lamps Are On, Brake Controller Illumination (Modify Brake Controller Wiring Harness) #02-05-22-004C - (Apr 5, 2005)

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

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

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

duanew1 · May 14, 2005

Thanks! I will try switching the wires when i get home today, because I did take the controller out of my 2000 chev 1/2 ton and plug it straight in to this new truck, without changing anything. Sounds like that might just work......I'll let you know.

This is the TSB I was thinking of, but it doesn't sound like it fits what you're talking about...

------------------------------

Trailer Brakes Applied When Headlights/Park Lamps Are On, Brake Controller Illumination (Modify Brake Controller Wiring Harness) #02-05-22-004C - (Apr 5, 2005)

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

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

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.

Pin

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.

Pin

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

© Copyright General Motors Corporation. All Rights Reserved.

<{POST_SNAPBACK}>

Bisek08 · August 26, 2008

I agree with the previous post... I am so glad I found this.

My Father in-law has the 2003 Silverado and the wiring harness for the 2002 model and his brake's symptoms were different, but dangerous:

The Light and the Stoplamps pins are reversed (per the earlier post). The person who installed the trailer brake module must have thought that the brake/lights pin was not connected and he kept the pin connector in place but also spliced the brake-switch wire to the same red wire.

Resulting symptoms:

- Drive with your lights on with the trailer and the brake is continuously engaged

- Drive without the trailer, but at night, and the brakelights of the truck are on all the time

- Drive without the trailer, during the day, all tail lights go on when braking

Do this long enough with the turn signal on during the day and a trailer and you will blow the fuse of the turn signal (I found that to be true for this truck at least)

I hope these symptoms help others who may run into this and don't make the link with the trailer brake.

asilverblazer · May 13, 2005

Did you use the factory harness?

duanew1 · May 13, 2005

Did you use the factory harness?

<{POST_SNAPBACK}>

Yes on the harness. I cut the factory plug end off and re-wired it to the 7 pin plug. Everything else works fine (lights, turn signals, brake lamps)

MRamsden · February 8, 2008

I have a 2005 Avalanche 5.3L I plugged it in and i got no power at the unit. what do i check to find out why I have no power? I have no manual

BurbanZ71 · February 8, 2008

Go to www.mygmlink.com and register. You can register without vin after you register they have a option to download manuals.

Then, find the section on fuses, most likely the trailer wiring fuse is either missing or blown.

Autox · April 24, 2007

I have a 2007 3500 Classic that has the same problem. I am guessing the 05/06 wiring is the same on the 07 classic?

My situation is that I have a Brakesmart controller that worked fine for a couple of months but quit responding when I step on the brake. While waiting for warranty support on the Brakesmart I put in a Prodigy I have. I bought an 06 wire plug and connected it up but it does the same sort of thing. It doesn't do anything at all with the lights off (meaning it doesn't apply any brakes). With the lights on the brakes are constant.

Something I noticed with the brakesmart is that the third brake light does not come on when I step on the brake pedal but if I manually activate the brakesmart then all the tail lights come on. I don't know if the prodigy does the same since I cannot use it after dark.

The red wire on the brakesmart harness plug and the prodigy harness plug are in different spots. I moved it on the prodigy plug to match the brakesmart plug but then the prodigy doesn't work at all lights on or off.

I am wondering if I have 2 problems. One with the red wire being in the wrong spot in the prodigy plug and one with the truck.

Any ideas? Thanks