General Description; System Components; Electronic Hydraulic Control Unit (Ehcu) . 5A-3 - Isuzu Trooper 1999 Workshop Manual

General Description

The Anti-lock Brake System (ABS) works on all four
wheels. A combination of wheel speed sensor and
Electronic Hydraulic Control Unit (EHCU) can determine
when a wheel is about to stop turning and adjust brake
pressure to maintain best braking.
Legend
(1) Electronic
(2) Hydraulic
(3) Electronic Hydraulic Control Unit (EHCU)

System Components

Electronic Hydraulic Control Unit (EHCU), four Wheel
Speed Sensors, Warning Light, and G-sensor.
Electronic Hydraulic Control Unit (EHCU)
The EHCU consists of ABS control circuits, fault detector,
and a fail-safe. It drives the hydraulic unit according to the
signal from each sensor, cancelling ABS to return to
normal braking when a malfunction has occurred in the
ABS.
The EHCU has a self-diagnosing function which can
indicate faulty circuits during diagnosis.
BRAKE CONTROL SYSTEM
This system helps the driver maintain greater control of
the vehicle under heavy braking conditions.
(4) Front Wheel Speed Sensor
(5) Rear Wheel Speed Sensor
(6) G-Sensor
(7) Proportioning and Bypass (P&B) Valve
The EHCU is mounted on the engine compartment front
right side. It consists of a Motor, Plunger Pump, Solenoid
Valves and Check Valve.
On the outside, the relay box containing a motor relay and
a valve relay is installed.
Solenoid Valves: Reduces or holds the caliper fluid
pressure for each front disc brake or both rear disc brakes
according to the signal sent from the EHCU.
Reservoir: Temporarily holds the brake fluid that returns
from the front and rear disc brake caliper so that pressure
of front disc brake caliper can be reduced smoothly.
Plunger Pump: Feeds the brake fluid held in the reservoir
to the master cylinder.
5A–3
C05RW002