2004 ISUZU TF SERIES sensor

BRAKE CONTROL SYSTEM 5A-3

DTC C0235 (Flash Code 35) Rear Left Wheel Speed Sensor Short Circuit or
Circuit Open .................................................................................................................... 5A-62
DTC C0236 (Flash Code 36) Rear Left Wheel Speed Sensor Incorrect Signal ............. 5A-64
DTC C0237 (Flash Code 37) Rear Left Wheel Speed Sensor Signal - Tooth
Chipping ........................................................................................................................... 5A-66
DTC C0238 (Flash Code 38) Tire Diameter Error ............................................................. 5A-68
DTC C0241 (Flash Code 41) Front Right Isolation Solenoid Circuit Open or
Shorted to Ground ........................................................................................................... 5A-69
DTC C0242 (Flash Code 42) Front Right Dump Solenoid Circuit Open or Shorted
to Ground.......................................................................................................................... 5A-69
DTC C0243 (Flash Code 43) Front Right Isolation Solenoid Circuit Shorted to
Battery............................................................................................................................... 5A-69
DTC C0244 (Flash Code 44) Front Right Dump Solenoid Circuit Shorted to
Battery............................................................................................................................... 5A-69
DTC C0245 (Flash Code 45) Front Left Isolation Solenoid Circuit Open or
Shorted to Ground ........................................................................................................... 5A-71
DTC C0246 (Flash Code 46) Front Left Dump Solenoid Circuit Open or Shorted
to Ground.......................................................................................................................... 5A-71
DTC C0247 (Flash Code 47) Front Left Isolation Solenoid Circuit Shorted to
Battery............................................................................................................................... 5A-71
DTC C0248 (Flash Code 48) Front Left Dump Solenoid Circuit Shorted to
Battery............................................................................................................................... 5A-71
DTC C0251 (Flash Code 51) Rear Isolation Solenoid Circuit Open or Shorted to
Ground .............................................................................................................................. 5A-73
DTC C0252 (Flash Code 52) Rear Dump Solenoid Circuit Open or Shorted to
Ground .............................................................................................................................. 5A-73
DTC C0253 (Flash Code 53) Rear Isolation Solenoid Circuit Shorted to Battery ......... 5A-73
DTC C0254 (Flash Code 54) Rear Dump Solenoid Circuit Shorted to Battery .............. 5A-73
DTC C0265 (Flash Code 65) Fail Safe Relay (FSR) Shorted to Ground ......................... 5A-75
DTC C0266 (Flash Code 66) Fail Safe Relay (FSR) Shorted to Battery.......................... 5A-75
DTC C0267 (Flash Code 67) ABS Motor Shorted to Ground .......................................... 5A-77
DTC C0268 (Flash Code 68) ABS Motor Shorted to Battery ........................................... 5A-77
DTC C0271 (Flash Code 71) ECU Failure or Valve +B Circuit Open .............................. 5A-79
DTC C0274 (Flash Code 74) ABS Operation Long Time ................................................. 5A-80
DTC C0276 (Flash Code 76) G-Sensor Malfunction ........................................................ 5A-82

5A-4 BRAKE CONTROL SYSTEM

DTC C0277 (Flash Code 77) Power Supply Low Input .................................................... 5A-84
DTC C0278 (Flash Code 78) Power Supply High Input ................................................... 5A-84
DTC C0282 (Flash Code 82) 4 Wheel Drive State Input Signal Failure .......................... 5A-86
DTC C0285 (Flash Code 85) Assembly Error (G-sensor) ................................................ 5A-88
Special Tools ...................................................................................................................... 5A-90


Service Precaution
WARNING: THIS VEHICLE HAS A SUPPLEMENTAL
RESTRAINT SYSTEM (SRS). REFER TO THE SRS
COMPONENT AND WIRING LOCATION VIEW IN
ORDER TO DETERMINE WHETHER YOU ARE
PERFORMING SERVICE ON OR NEAR THE SRS
COMPONENTS OR THE SRS WIRING. WHEN YOU
ARE PERFORMING SERVICE ON OR NEAR THE
SRS COMPONENTS OR THE SRS WIRING, REFER
TO THE SRS SERVICE INFORMATION. FAILURE TO
FOLLOW WARNINGS COULD RESULT IN
POSSIBLE AIR BAG DEPLOYMENT, PERSONAL
INJURY, OR OTHERWISE UNNEEDED SRS SYSTEM
REPAIRS.



CAUTION: Always use the correct fastener in the
proper location. When you replace a fastener, use
ONLY the exact part number for that application.
ISUZU will call out those fasteners that require a
replacement after removal. ISUZU will also call out
the fasteners that require thread lockers or thread
sealant. UNLESS OTHERWISE SPECIFIED, do not
use supplemental coatings (Paints, greases, or
other corrosion inhibitors) on threaded fasteners or
fastener joint interfaces. Generally, such coatings
adversely affect the fastener torque and the joint
clamping force, and may damage the fastener.
When you install fasteners, use the correct
tightening sequence and specifications. Following
these instructions can help you avoid damage to
parts and systems.

BRAKE CONTROL SYSTEM 5A-5

General Description
EHCU has controlled ABS (Anti-lock Brake System)
and EBD (Electronic Brake-force Distribution System).
ABS works on all four wheels. EBD system works on
rear 2 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. This system helps the driver maintain greater control of
the vehicle under heavy braking conditions.

Note: The Electronic Hydraulic Control Unit (EHCU)
comprises the Hydraulic Unit (H/U) and Control Unit.













This illustration is based on RHD model
C05L300010
Legend

(1) Electronic (6) Front Left Wheel Speed Sensor
(2) Hydraulic (7) Rear Right Wheel Speed Sensor
(3) Hydraulic Unit (H/U) (8) Rear Left Wheel Speed Sensor
(4) Control Unit (9) G-sensor (4WD only)
(5) Front Right Wheel Speed Sensor (10) 2-4WD Control Unit (4WD only)

BRAKE CONTROL SYSTEM 5A-9

Pressure Isolation (Pressure Maintain)
The electronic-hydraulic control unit is activated when
the brakes are applied.
If the information from the wheel speed sensors
indicates excessive wheel deceleration (imminent
lockup), the first step in the anti-lock sequence is to
isolate the brake pressure being applied by the brake
pedal.
The microprocessor in the Control Unit sends a voltage
to the coil to energize and close the isolation valve.
This prevents any additional fluid pressure applied by
the brake pedal from reaching the wheel. With the
isolation valves closed, unnecessary increase in the
brake pressure is prevented.
C05L300013

BRAKE CONTROL SYSTEM 5A-13

Connector List
No. Connector face No. Connector face
B-23
Green
Meter-A C-44
WhiteStop Light Switch
B-24
Green
Meter-B C-53
OrangeABS Sensor Front-RH
B-48
Black
G-sensor C-54
OrangeABS Sensor Front-LH
B-54
White
I2 C-67
BlackEHCU
B-56
White
J/B I4 C-107
WhiteJ/B E2
B-58
Black
Data Link Connector C-108
WhiteJ/B E1
B-62
White
Ignition Switch (IGSUB : G1) C-109
SilverBody-LH ; Ground
B-63
White
Ignition Switch (IGSUB : G2) F-4
Gray ABS Sensor Rear
C-2
Silver
Engine Room-RH ; ground H-6
WhiteEngine Room ~ INST
C-36
Silver
Engine Room-LH ; Ground H-7
WhiteEngine Room ~ INST

BRAKE CONTROL SYSTEM 5A-17

EHCU Pin-outs


C05L300005

EHCU Side
Pin No.
(Harness
side
Pin No.) Pin Function Wire
Color Typical Value Note
1
(C67-11) Power Supply WHT/GRN Battery Voltage Solenoid
2
(C67-10) Ground 1 BLK 0V
(Less than 0.1V) Solenoid, Control Unit
3
(C67-28) Ground 2 BLK 0V
(Less than 0.1V) Motor
4
(C67-27) Power Supply WHT/RED Battery Voltage Motor
5
(C67-9) Stop Light Switch RED Open : 0V
Close : Battery Voltage Close Condition :
Step on the Brake Pedal
6
(C67-8) Serial ORN/WHT - J1850 Class 2
Communication
7
(C67-7) Serial GRN - J1850 Class 2
Communication
8
(C67-6) Not Used - -
9
(C67-5) Not Used - -
10
(C67-4) G-Sensor Ground BLK 0V
(Less than 0.1V) 4WD Only
DTC C0276, C0285
11
(C67-3) Front Right Wheel Speed Sensor (-) GRY High Level: 1.28~2.2V
Low Level: 0.5~0.86V DTC C0221,C0222,
C0223
12
(C67-2) Front Right Wheel Speed Sensor (+) GRY/RED 12

1.5V DTC C0221,C0222,
C0223
13
(C67-1) Rear Right Wheel Speed Sensor (-) BLK High Level: 1.28~2.28V
Low Level: 0.5~0.86V DTC C0231,C0232,
C0233

5A-18 BRAKE CONTROL SYSTEM

EHCU Side
Pin No.
(Harness
side
Pin No.) Pin Function Wire
Color Typical Value Note
14
(C67-17) ABS Warning Lamp YEL More than 10V
15
(C67-16) Not Used - -
16
(C67-15) Not Used - -
17
(C67-14) G-Sensor Signal YEL/BLK 2.0~3.0V
(MAX4.0V,MIN1.0V) 4WD Only
It checks in a flat place
(0G:2.5V)
DTC C0276, C0285
18
(C67-13) Front Left Wheel Speed Sensor (+) RED 12

1.5V DTC C0225, C0226,
C0227
19
(C67-12) Rear Right Wheel Speed Sensor (+) ORN 12

1.5V DTC C0231,C0232,
C0233
20
(C67-26) EBD (Brake) Warning Lamp LT BLU More than 10V
21
(C67-25) Starter Switch ON
(Power Supply and Switch Position) BLU/WHT Battery Voltage Control Unit
DTC C0277,C0278
22
(C67-22) Not Used - -
23
(C67-23) Not Used - -
24
(C67-22) Not Used - -
25
(C67-21) Transfer (2-4WD Control Unit) GRY Pulse Signal
(High 4.5V, Low 1.5V) 4WD Only
DTC C0282
26
(C67-20) Front Left Wheel Speed Sensor (-) WHT High Level: 1.28~2.2V
Low Level: 0.5~0.86V DTC C0225, C0226,
C0227
27
(C67-19) Rear Left Wheel Speed Sensor (+) GRY/BLU 12

1.5V
DTC C0235, C0236,
C0237
28
(C67-18) Rear Left Wheel Speed Sensor (-) WHT/BLU High Level: 1.28~2.2V
Low Level: 0.5~0.86V DTC C0235, C0236,
C0237

BRAKE CONTROL SYSTEM 5A-19

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 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


825L300001
Vehicles equipped with the Anti-lock Brake System
have an amber “ABS” warning lamp in 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
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
to the “ON” position.
If the “ABS” warning lamp stays “ON” after the ignition
switch is 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
diagnosis 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
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 features 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.