A braking system including a wheel brake with a dual piston caliper assembly provides a brake by wire add-on system with dual level manual override capabilities. A pressure control block associated with the wheel brake directs fluid pressure generated by the master cylinder to the first and the second pistons of the caliper assembly for operation of the braking system in a manual apply mode. An electro-hydraulic modulator generates operating pressure in the brake by wire mode. The electro-hydraulic modulator communicates with the pressure control block so that fluid pressure generated by the electro-hydraulic modulator is transmitted to a single piston of the caliper assembly and is prevented from being communicated to the first piston of the caliper assembly by a solenoid valve assembly positioned in the pressure control block.