Pressure Drop
The control module de-energizes the inlet and outlet valves. This returns the brake circuit back to normal braking and the hydraulic pressure is once again determined by the driver's pedal force.
This sequence continues rapidly until the wheel speed signals are once again acceptable and the contact of the road and the tire surfaces are restored.
When the system is in regulation, the brake pedal could progressively sink to the floor. This would be the result of bleeding hydraulic pressure during ABS regulation.
The return pump maintains the pressure between the master cylinder and the inlet valve to prevent the pedal from sinking completely to the floor.
This entire sequence of events happens repeatedly in a split second. The function of the pump is felt in the brake pedal during ABS regulation.
With the inlet valve closed the pressure on the caliper is stabilized and isolated. The control module energizes the outlet valve which opens the outlet port and drops the pressure in the isolated portion of the circuit.
The brake fluid flows back to the master cylinder reservoir.