Circuit description
WARNING: This page is about a different car, the 2018 Subaru BRZ. However, it is still accessible from the selected car via links, so may be relevant.
When the brake pedal is released, ECM terminal BRK1 receives positive (+) battery voltage through IG2 fuse. While the brake pedal is depressed, the stop light switch sends signals to ECM terminal BRK1 and BRK2. When terminal BRK1 receives the signal, ECM cancels the cruise control driving.