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goodwrench9124, ASE Certified Technician
Category: Chevy
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Experience:  Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
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Where does the electric trailer brakes get its power from ...

Resolved Question:

Where does the electric trailer brakes get its power from when the truck brakes are applied on a 2007 Chev Silverado 2500 HD?
Submitted: 9 years ago.
Category: Chevy
Expert:  goodwrench9124 replied 9 years ago.

hello, gm has changed their 07 brake controller wiring. i will include some instructions that should help you. and anything you dont understand please ask me to explain.


Some owners may notice that there is no power at the Auxiliary power terminal of the 7-way trailer connector. Circuit 742 Red/Black is the power feed to the 7-way connector.


To have power at the 7-way connector, circuit 742 must be connected to Stud 1 (40 Amp Fuse) of the UBEC. The wire is taped to the engine/chassis harness under the master cylinder near the I-shaft.

Object Number:(NNN) NNN-NNNN Size: SH

  1. Circuit 242 (Used to power aftermarket trailer brake controller-Blunt cut end under dash near DLC)
  2. Circuit 742 (Used to power 7-way trailer connector for Auxiliary Power to trailer)
  3. Stud 2
  4. Stud 1

Note: Do not confuse 742 with circuit 242 (Doc ID(NNN) NNN-NNNN which is used to power an aftermarket trailer brake controller. When installing an aftermarket trailer brake controller, circuit 242 must be connected to Stud 2 (30 Amp Fuse) of the UBEC. This circuit is taped to the engine harness between the UBEC and Left Fender. More information on this can be found in Bulletin 06-08-45-008.

Subject:Information on Electric Trailer Brake Controller Wiring - Towing, Tow #06-08-45-008 - (10/10/2006)


Models:2007 Cadillac Escalade, Escalade ESV, Escalade EXT
2007 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2007 GMC Sierra, Yukon, Yukon Denali, Yukon XL, Yukon Denali XL


Some customers may have questions on how to connect an electric trailer brake controller or where the brake controller pigtail harness is located.

Starting with the new 2007 full size utilities and pickups, there is no longer an electric trailer brake controller pigtail harness.

The trailer brake controller wiring is now part of the Instrument panel wiring harness and the blunt cut wires are located under the left instrument panel, behind the data link connector. There are four blunt cut wires in this harness as described below.

Wire Color

Circuit #




12 Volt power supply (30A stud #2)

Dark Blue


Trailer brake output voltage




Light Blue


Stop light input

Object Number:(NNN) NNN-NNNN Size: SH

The Red/Black circuit 242 must be connected to stud #2 of the 30 Amp fuse of the UBEC. This wire is located between the left fender and the UBEC (1). Refer to Trailer Connector/Provision Schematic in SI for document information on the trailer brake control-- Domestic.


goodwrench9124 and 2 other Chevy Specialists are ready to help you
Customer: replied 9 years ago.
Relist: I still need help.
This is 2007 Silverado Classic...or 2006 Model. Recently installed brake box, everything working fine, then the brake box quit receiving power when the brake pedal was applied. Need to know if there is a relay or does it get its power from the brake light switch? The wire that used to apply 12 volts when brake pedal depressed stopped having 12 volts on it. When brakes are not applied there is a ground; when brakes are applied there is not 12 volts present. Help!
Expert:  goodwrench9124 replied 9 years ago.

the lt blue wire is the 12v brake imput from CHMSL PCB relay which is turn off and off by the bcm, i have included wiring diagram, also check the fuse for CHMSL PSB

Stop Lamp Controls and CHMSL

Object Number:(NNN) NNN-NNNN Size: FS

goodwrench9124 and 2 other Chevy Specialists are ready to help you