The ABS (Antilock Brake System) controls the fluid pressure applied to the wheel cylinder of each brake from the
master cylinder so that each wheel is not locked even when hard braking is applied.
This ABS has also the following function.
While braking is applied, but before ABS control becomes effective, braking force is distributed between the front and
rear so as to prevent the rear wheels from being locked too early for better stability of the vehicle.
The main component parts of this ABS include the following parts in addition to those of the conventional brake
• Wheel speed sensor which senses revolution speed of each wheel and outputs its signal.
Rear wheel speed sensor of 4WD vehicle is integrated in rear wheel hub assembly and supplied as rear wheel hub
Front wheel speed sensor and rear wheel speed sensor of 2WD model are separated from wheel hub assembly
and supplied as spare parts.
• ABS warning light which lights to inform abnormality when system fails to operate properly.
• ABS hydraulic unit / control module assembly is incorporated ABS control module, ABS hydraulic unit (actuator
assembly), solenoid valve power supply driver (transistor), solenoid valve driver (transistor), pump motor driver
– ABS control module which sends operation signal to ABS hydraulic unit to control fluid pressure applied to each
wheel cylinder based on signal from each wheel speed sensor so as to prevent wheel from locking.
– ABS hydraulic unit which operates according to signal from ABS control module to control fluid pressure applied
to wheel cylinder of each 4 wheels.
– Solenoid valve power supply driver (transistor) which supplies power to solenoid valve in ABS hydraulic unit.
– Solenoid valve driver (transistor) which controls each solenoid valves in ABS hydraulic unit.
– Pump motor driver (transistor) which supplies power to pump motor in ABS hydraulic unit.
• G sensor which detects body deceleration speed for 4WD model.
This ABS is equipped with Electronic Brake force Distribution (EBD) system that controls a fluid pressure of rear
wheels to best condition, which is the same function as that of proportioning valve, by the signal from wheel sensor
independently of change of load due to load capacity and so on. And if the EBD system fails to operate properly, the
brake warning light lights to inform abnormality.