Not 100% sure but I believe the signal required for braking function will be provided by the brake pedal switch to the vehicle ECU . There is a control of some sort attached to the ABS pump which is in the engine bay, follow the brake pipes.
The brake ECU is part of the ABS module located in the engine compartment. As @joka250 says, follow the hydraulic brake lines to where they all connect to a rectangular box with a cylindrical projection. The loom from the ABS module runs to the body computer.