Isuzu N-Series. Manual - part 258

5A4-6 ABS/ASR

System Component

Component location

Legend

1. Rear speed sensor RH
2. Rear speed sensor LH
3. LSPV
4. EHCU
5. Front speed sensor LH

6. Engine control unit
7. Self-diagnosis connector
8. ABS/ASR warning lamp
9. Front speed sensor RH

N5A2003E

ABS/ASR 5A4-7

Electronic Hydraulic Control Unit (EHCU)

Legend

1. Electronic control unit part
2. Hydraulic control unit part

EHCU consists of ECU and HU. The ECU consists of
the ABS/ASR control part, the fault detecting part, and
the fail-safe part. It drives the hydraulic unit etc. based
on the signal transmitted from each sensor. In case of
system failure, it stops the fail-safe and returns to the
normal brake. Also, the self-diagnosis function is
equipped to indicate the trouble part during diagnosis.

The HU consists of the motor, the plunger pump, and
the solenoid valve.
Solenoid valve: Decrease, hold, increase the brake fluid
pressure based on the signal transmitted from the ECU.
Reservoir: Temporarily store the brake fluid from each
caliper to lower the fluid pressure smoothly.
Plunger pump: Send the brake fluid stored in the reser-
voir to the master cylinder.
Motor: Drive the plunger pump based on the signal from
ECU.
Check valve: Control the brake fluid flow.

CAUTION:

Turning the key ON with the harness disconnected from
the EHCU means that the CAN communication line is
not connected at this moment. Therefore, the systems
which perform CAN communication such as engine and
Smoother are judged as faulty. After replacing the EH-
CU, clear the DTCs of the systems which perform CAN
communication. Also, do not drive the vehicle with the
EHCU removed.

N5A2004E

5A4-8 ABS/ASR

Wheel Speed Sensor

Front speed sensor

Legend

1. Electrode
2. Sensor
3. Sensor rotor

Rear speed sensor

Legend

1. Sensor
2. Sensor rotor

The front speed sensor consists of permanent magnet
and coil, and the rear speed sensor is the 2 wire system
hall IC type and is installed to the knuckle for front
wheels, and to the brake back plate for rear wheels.
Sensor rotors inserted in front/rear wheel hubs rotate to
generate voltage in the sensor. Frequency of this volt-
age varies in relation to the rotor revolution speed;

therefore this allows the sensor to detect the vehicle
speed.

ABS Warning Lamp

The ABS warning lamp comes on with the starter switch
ON, and then goes off if the ABS is normal.
It also comes on in case of ABS malfunction, and indi-
cates the trouble code with blinking pattern upon change
of the EHCU to diagnosis mode.

ASR Indicator/Off Lamp

The ASR warning lamp comes on with the starter switch
ON, and then goes off if the ASR is normal.
It blinks while the ASR is in operation.
It comes on in case of ASR malfunction and when the
ASR off switch is pressed to deactivate the system.
It indicates the trouble code with blinking pattern upon
changing to the diagnosis mode.

CAUTION:

When either of the ABS or ASR is faulty (which does not
affect the other), the warning lamp of the affected sys-

N5A2005E

N5A2006E

N5A2007E

N5A2007E

ABS/ASR 5A4-9

tem only comes on and prohibit the system operation.
In this case, the other system is still workable if normal.

ASR Off Switch

Pressing the ASR off switch after starting the engine de-
activates the ASR, and pressing again bring the system
to stand-by condition. The ASR is set stand-by condition
whenever the engine is started regardless of switch con-
dition.

N5A2008E