Location of the CHMSL Circuit on a 2012 Chevy Silverado for a Camper Shell Third Brake Light

Updated 10/07/2025 | Published 11/26/2012

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Question:

Hi Ive got a 2012 silverado 2500 hd with towing package and integrated trailer brake. Want wire up cap lighting Is there a point in which to wire behind or under space by installed hitch?

asked by: Erik H

Expert Reply:

There is a bundle of wires under the brake pedal of your 2012 Chevy Silverado that will have an orange wire that should be used to power the third brake light of the camper shell. I have also read that the light blue wire under the rear of your vehicle in the harness near the trailer connector will also work, but I would recommend you use a circuit tester like our # PTW2993 to make sure that this wire only sees voltage when the brakes are applied and none when the blinkers are on without the brakes.

Check out the FAQ article I attached that will show where the CHMSL wire is.

expert reply by: Jameson C

Chandler

10/7/2025

I have dark blue light green dark green yellow and brown no light blue wire

Jameson C.

10/7/2025

@Chandler Do you have a circuit tester like the part # PTW2993? I would probe all of the wires till you find the one that has voltage only when brakes are applied.

Chandler

10/7/2025

@JamesonC we have tried all the brake light wires and trailer hitch wires on this 2012 Silverado with computerized brake. The canopy light blinks when we turn on the blinker when hooked to any of those wires

Jameson C.

10/7/2025

@Chandler We have a way to create a dedicated brake light switch with the part # RM-751000 or you could tap into the wire that runs to the third brake light on the truck if that circuit just isn't in that wiring bundle.