Where is Stoplight Circuit Found on 2015 Chevy Sonic for SMI DUO Install

Question:

I will be towing my 2015 Sonic 5 speed manual hatch back. I have installed SMI Duo aux braking system as well as Trailer Mate TM780098S light wiring harness. My motorhome has combined brake/turn lights. I am assuming I need a Roadmaster 88400 brake light relay. The Sonic has a brake pedal position sensor rather than a brake light switch. Is the brake light relay installation the same? The position sensor has three wires. Black, white, and blue with yellow stripe. Which wire do I splice the relay into? Access to the sensor is very limited so I am unable to reach with a test light check which wire is cold.

asked by: Martin H

Expert Reply:

You are in luck as we had the chance to install the SMI DUO part # SM99251 in a 2014 Chevy Sonic very similar to your 2015 model. I attached a video that shows the entire install process. In it you'll see that instead of tapping into the stoplight circuit of the vehicle they use the blue output wire on the operating unit instead.

expert reply by: Jameson C