How To Connect Trailer Brake Controller To Cold Side Of Stoplight Switch In 2020 GMC Terrain

Updated 06/07/2021 | Published 06/04/2021

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Hook Probe Circuit Tester

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Quick Splices - Self-Stripping Connector - Closed Port - 14-16-18 Gauge - Blue - Qty 1

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Question:

Brake controller install on a 2020 GMC Terrain. I've heard you can't just go into the stop light wire like usual. Is this true? So what's the alternative?

asked by: Dan

Expert Reply:

You are correct. On your 2020 GMC Terrain connecting a trailer brake controller harness is a bit different as you cannot just connect the red stoplight wire directly to the cold side wire of the stop light switch.

The work around for this is you will need to pick up the cold side wire in the BCM (Body Control Module) of your Terrain. The BCM is located between the emergency brake pedal and brake pedal about where your left knee is when sitting in the driver seat as shown in the included diagram.

You will need to use a quick splice like # SWC502905-1 to connect the red stoplight wire from your trailer brake controller harness to the white wire at the number 11 position of the BCM plug which is shown in the included diagram. This will connect your controller to the cold side of the stop light switch which only has power when the brake pedal is pressed.

I included a link to a helpful article on installing a trailer brake controller for you to take a look at as well.

expert reply by: Samuel C