Isuzu 1999 RODEO Workshop Manual page 382

Pressure Reduction
Once the brake pressure is isolated, it must be reduced to
allow the wheels to unlock. This is accomplished by
dumping a portion of the brake fluid pressure into a low
pressure accumulator.
The microprocessor activates the normally closed dump
valve to open, allowing fluid from the wheels to be
dumped into the accumulator. This is done with very short
activation pulses opening and closing the dump valve
passageway. Brake pressure is reduced at the wheel and
allows the wheel to begin rotating again. The fluid from the
brake piston is stored in the accumulator against spring
pressure and a portion of this fluid also primes the pump.
Legend
(1) Brake
(2) Master Cylinder
BRAKE CONTROL SYSTEM
The dump valves are operated independently to control
the deceleration of the wheel. At this point, the brake
pedal is isolated from the base brake system, the
hydraulic control unit pumps are primed and the
attenuators are ready to pump fluid.
5A–7
C05RW009