Normal Braking And Pressure Increase

Fig 1: Pressure Retention & Pressure Reduction Valve Positions - Normal Braking Pressure Increase

Courtesy of MAZDA MOTORS CORP.

During normal braking and increase in pressure, current does not flow to the coils. The valve spring presses on the armature, causing the pressure retention valve to open and the pressure reduction valve to close.
The passage to the reservoir is blocked because the pressure reduction valve is closed. As a result, the brake fluid passes through the pressure retention valve and acts on the calipers.
A rubber cup is fitted to the pressure retention valve. The function of this cup enables the brake fluid to return smoothly from the calipers to the master cylinder side when the brake pedal is released.