Tech Tip: Installing an Aftermarket Trailer Brake Controller

Some customers with the following vehicles may ask to have an aftermarket trailer brake controller added to their vehicle, or to have one installed in lieu of their factory brake controller (RPO JL1):
• 2015–2020 Cadillac Escalade
• 2014 Chevrolet Silverado 1500
• 2015–2018 Silverado
• 2019 Silverado LD
• 2019 Silverado 2500/3500
• 2015–2020 Suburban
• 2015–2020 Tahoe
• 2014 GMC Sierra 1500
• 2015–2018 Sierra
• 2019 Sierra Limited
• 2019 Sierra 2500/3500
• 2015–2020 Yukon models
To install an aftermarket brake controller on one of those vehicles, follow these steps:

Step 1 : Obtain a trailer brake controller harness (#23184088) as shown in the photo.

Step 2: Connect the harness to the MIDBEC (X61A), which is located under the instrument panel to the left of the steering column. The harness connection point (1) is shown in the illustration below.

Step 3: The harness consists of four blunt-cut wires and a label that calls out the wire colours and each wire’s function (see chart below). Use these wires to connect to the aftermarket trailer brake controller.

Step 4: Perform the following step ONLY if the vehicle is equipped with the RPO JL1 (the factory-integrated trailer brake controller) and the customer is requesting that the factory trailer brake system be bypassed for an aftermarket trailer brake controller: Locate connector X185 or X138 (varies with vehicle build; refer to Service Information), which is near the underhood fuse block, terminal 32. Circuit 47 ends at the body harness side of X185/ X138 terminal 32, which comes from the X61A junction block.

Step 5: Obtain enough Dark Blue 12-gauge wire to run from X185/X138 to the 7-way trailer connector at the bumper. Attach the terminated lead (#13327155) to one end of the Dark Blue wire and insert into the chassis harness side of the X185/ X138 connector terminal 32.

Step 6: Run the Dark Blue wire through its own conduit along the frame to the 7-way trailer connector at the bumper. Remove circuit 47 from the 7-way trailer connector terminal “C” and then tape the bare terminal and attach it to the harness.

Step 7: Attach the terminal (#12110853) located in Delphi Tray 4 to the other end of the Dark Blue wire with the correct weather pack seal, and insert it into the 7-way trailer connector terminal “C.”
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