Although your's may not exhibit this condition, the technical bulletin may help.
Bulletin No.: 02-05-22-004C
Date: April 05, 2005
Trailer Brakes Applied When Headlights/Park Lamps Are On, Brake Controller Illumination (Modify Brake Controller Wiring Harness)
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
This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 02-05-22-004B (Section 05 - Brakes).
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.
The cause of this condition may be due to wiring changes within the vehicle electrical system for the 2003 model year.
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 This number has been superseded to 15366255, with a pink/purple tag identifier of 6255.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 information shown is for the 1999-2002 wiring harnesses and for the 2003-05 wiring harness.
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".
When the correct wiring harness P/N is matched to the specific model year of the vehicle, everything works properly.
I'll forward you a bit more shortly.