ABS System Description - ABS Modulator
The ABS modulator unit consists of the inlet solenoid valve, the outlet solenoid valve, the reservoir, the pump, and the pump motor. The hydraulic control has three modes of ABS action; pressure intensifying, pressure retaining, and pressure reducing.

Mode
Inlet Solenoid
Valve
Outlet Solenoid
Valve
Brake Fluid
Pressure intensifying mode
open
closed
Master cylinder fluid is pumped out to the caliper.
Pressure retaining mode
closed
closed
Caliper fluid is retained by the inlet and outlet valves.
Pressure reducing mode
closed
open
Caliper fluid flows through the outlet valve to the reservoir.
The motor pumps the reservoir fluid through the master cylinder.