Acura 3.5 RL Manual page 837

Anti-lock Brake System (ABS)
Features/Construction (cont'd)
ABS Modulator
The ABS modulator consists of the inlet solenoid valve, outlet solenoid valve, reservoir, pump, pump motor and the
damping chamber.
The modulator reduces the caliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates
through the caliper, reservoir and the master cylinder.
The hydraulic control has three modes: pressure reduction, pressure retaining and pressure intensifying.
The hydraulic circuit is the independent four channel-type, one channel for each wheel.
PUMP
MOTOR
Pressure intensifying mode: Inlet valve open, outlet valve closed
Pressure retaining mode:
Pressure reduction mode:
Motor operation mode:
Master cylinder fluid is pumped out to the caliper.
Inlet valve closed, outlet valve closed
Caliper fluid is retained by the inlet valve and outlet valve.
Inlet valve closed, outlet valve open
Caliper fluid flows through the outlet valve to the reservoir.
When starting the pressure reduction mode, the pump motor is ON.
When stopping ABS operation, the pump motor is OFF.
The reservoir fluid is pumped out by the pump, through the damping chamber, to the master
cylinder.
SOLENOID VALVE
IN:
OUT: OUTLET VALVE (NORMALLY CLOSED)
INLET VALVE (NORMALLY OPEN)