Isuzu KB P190. Manual - part 153

BRAKE CONTROL SYSTEM   5A-19 

Parts Location (LHD) (2) 

 

 

 

 

RTW78AXF047001 

 

5A-20   BRAKE CONTROL SYSTEM 

EHCU Pin-Assignment 

 

 

 

RTW75ASF000101 

 

EHCU Side  

Pin No. 

Pin Function 

Wire Color

Typical Value 

Note 

1 Ground 

1 

BLK 

0V 

(Less than 0.1V) 

Motor 

2 

Power Supply 

WHT/RED

Battery Voltage 

Motor 

3 

Power Supply 

WHT/GRN

Battery Voltage 

Solenoid 

4 Ground 

2 

BLK 

0V 

(Less than 0.1V) 

Solenoid, 

Control Unit 

5 

Front Left Wheel Speed Sensor (-) 

WHT 

High Level: 0.8~1.3V 

Low Level: 0.4~0.7V 

DTC C0225, C0226 

6 

Rear Left Wheel Speed Sensor (+) 

WHT/BLU

12±1.5V 

DTC C0235, C0236 

7 

Rear Right Wheel Speed Sensor (+) 

ORN 

12±1.5V 

DTC C0231, C0232 

8 

Rear Right Wheel Speed Sensor (-) 

BLK 

High Level: 0.8~1.3V 

Low Level: 0.4~0.7V 

DTC C0231, C0232 

9 

Front Right Wheel Speed Sensor (+) 

BRN 

12±1.5V 

DTC C0221, C0222 

10 

Front Right Wheel Speed Sensor (-) 

LT 

GRN/BLK

High Level: 0.8~1.3V 

Low Level: 0.4~0.7V 

DTC C0221, C0222 

11 Serial 

VIO/GRN

- 

Keyword 

2000 

12 

EBD (Brake) Warning Lamp 

LT BLU 

More than 10V 

- 

13 Not 

Used  - 

- 

- 

14 

G Sensor Ground 

YEL/GRN

0V 

(Less than 0.1V) 

4WD Only 

DTC C0276, C0285 

15 Not 

Used  - 

- 

- 

16 

Front Left Wheel Speed Sensor (+) 

RED 

12±1.5V 

DTC C0225, C0226 

17 

Rear Left Wheel Speed Sensor (-) 

WHT/BLU

High Level: 0.8~1.3V 

Low Level: 0.4~0.7V 

DTC C0235, C0236 

18 

Starter Switch ON 

(Power Supply and Switch Position) 

BLU/WHT

Battery Voltage 

Control Unit 

DTC C0277, C0278 

19 Not 

Used  - 

- 

- 

BRAKE CONTROL SYSTEM   5A-21 

EHCU Side  

Pin No. 

Pin Function 

Wire Color

Typical Value 

Note 

20 

Stop Light Switch 

RED 

Open: 0V 

Close: Battery Voltage 

Close Condition: 

Step on the Brake 
Pedal 

21 

G Sensor Signal 

YEL/BLK

2.0~3.0V 

(MAX 4.0V, MIN 1.0V) 

4WD Only 

It checks in a flat place 
(0G: 2.5V) 

DTC C0276, C0285 

22 

ABS Warning Lamp 

YEL 

More than 10V 

- 

23 Not 

Used  - 

- 

- 

24 

Transfer (2-4WD Control Unit) 

GRY 

Pulse Signal 

(High 4.5V, Low 1.5V) 

4WD Only 

DTC C0282 

25 

Serial 

ORN/WHT

- 

Short to GND: 

Flash out DTCs 

26 Not 

Used  - 

- 

- 

 

5A-22   BRAKE CONTROL SYSTEM 

System Components 

Electronic Hydraulic Control Unit (EHCU), four Wheel 
Speed Sensors, two Warning Lamps, and G sensor. 

 

Electronic Hydraulic Control Unit (EHCU) 

The EHCU consists of ABS control circuits, fault 
detector, and a fail-safe. It drives the EHCU 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. 

The EHCU is mounted on the engine compartment rear 
left side. It consists of a motor, solenoid valves and a 
fail safe relay. 

Solenoid Valves: Reduces or holds the caliper fluid 
pressure for each front brake or both rear brakes 
according to the signal sent from the EHCU. 

Buffer chamber: Temporarily holds the brake fluid that 
returns from the front and rear brake so that pressure of 
front brake can be reduced smoothly. 

Motor: Drives the pump according to the signal from 
EHCU. 

Fail safe Relay: When failure occurs in ABS. 

The power supply to solenoid Valve is cut. 

 

ABS Warning Lamp 

 

 

RTW75ASH000101

Vehicles equipped with the Anti-lock Brake System 
have an amber “ABS” warning lamp on the instrument 
panel.  The “ABS” warning lamp will illuminate if a 
malfunction in the Anti-lock Brake System is detected 
by the Electronic Hydraulic Control Unit (EHCU). In the 
case of an electronic malfunction, the EHCU will turn 
“ON” the “ABS” warning lamp and disable the anti-lock 
braking function. 

 

 

The “ABS” warning lamp will turn “ON” for 
approximately three seconds after the ignition switch is 
in the “ON” position. 

If the “ABS” warning lamp stays “ON” after the ignition 
switch is in the “ON” position, or comes “ON” and stays 
“ON” while driving, the Anti-lock Brake System should 
be inspected for a malfunction according to the 
diagnostic procedure. 

 

Wheel Speed Sensor (WSS) 

It consists of a sensor and a rotor.  The sensor is 
attached to the knuckle on the front wheels and to the 
rear wheels. 

The rotor is press-fit in the axle shaft. 

 

G Sensor 

The G sensor detects the vehicle deceleration speed 
and sends a signal to the EHCU.  In 4WD operation, all 
four wheels may be decelerated in almost the same 
phase, since all wheels are connected mechanically. 

This tendency is noticeable, particularly on roads with 
low friction coefficient, and the ABS control is adversely 
affected. 

The G sensor judges whether the friction coefficient of 
the road surface is low or high, and changes the 
EHCU's operating system to ensure ABS and EBD 
control. 

 

Normal and Anti-lock Braking 

Under normal driving conditions, the Anti-lock Brake 
System functions the same as a standard power 
assisted brake system. However, with the detection of 
wheel lock-up, a slight bump or kick-back will be felt in 
the brake pedal. This pedal “bump” will be followed by a 
series of short pedal pulsations which occurs in rapid 
succession.  The brake pedal pulsation will continue 
until there is no longer a need for the anti-lock function 
or until the vehicle is stopped. A slight ticking or popping 
noise may be heard during brake applications when the 
anti-lock feature is being used. 

When the anti-lock feature is being used, the brake 
pedal may rise even as the brakes are being applied.  
This is also normal.  Maintaining a constant force on the 
pedal will provide the shortest stopping distance.