You can retract or extend the EPB piston by hooking up 12v power source to the contacts inside of the plug of the EPB motor. On the Performance red caliper the plug is square on one side. To retract the inner piston, connect (-) ground to the contact close to the square side while connect (+) to the contact at the round end of the plug. To extend the inner piston, switch the polarity. There is no auto stop on the motor, so pay attention to the sound of the motor when it is at end of its travel on retraction. Break the circuit when you hear the sound change.