Pressure Reduction

Fig 1: Pressure Retention & Pressure Reduction Valve Positions - Pressure Reduction

Courtesy of MAZDA MOTORS CORP.

When pressure is being reduced, current flows to the pressure retention valve and the pressure reduction valve.
The magnetic force generated in the coil by the current enables the armature to overcome the force of the valve spring.
As a result, the armature moves, closing the pressure retention valve and opening the pressure reduction valve.
When the pressure reduction valve opens, the passage between the reservoir and the brake caliper opens. This makes the pressure of the brake fluid on the caliper pass in to the reservoir. As a result, pressure is reduced.
The pressure reduction signal also causes the pump to operate, transferring the hydraulic fluid within the reservoir to the damper.