Isuzu N-Series. Service manual — part 257
5A4-2 ABS/ASR
ABS/ASR System
Description of Function and Operation
Description of ABS/ASR
ABS (Anti-lock Brake System) and ASR (Anti-Slip Reg-
ulator) are the system to prevent the wheels from lock-
ing and wheel spin, and to assure stability and steering
ability of the vehicle.
When a malfunction occurs in the system, fail-safe de-
activate the ABS and ASR, and the warning lamp comes
on. Also, the self-diagnosis function is equipped to im-
prove serviceability.
Contents of ABS Control
The ABS controls the brake fluid pressure in the way
that the electronic hydraulic control unit (EHCU) hold/
decrease/increase the brake fluid pressure during brake
operation, based on the signal transmitted from the
wheel speed sensor.
The EHCU calculate the wheel speed, the wheel accel-
eration speed, and the vehicle speed based on the sig-
nal transmitted from the wheel speed sensor. When
brake is applied while the vehicle is running, the wheel
speed abruptly goes down, and the difference from the
vehicle speed becomes more than specified; the EHCU
judges that the wheel turns toward being locked, and it
performs holding of the brake fluid pressure.
When the vehicle speed further goes down, the system
judges that the wheel is about to be locked, and it per-
forms decreasing of the brake fluid pressure. Conse-
quently, when the system judges that wheel lock is
avoided, it performs holding and increasing of the brake
fluid pressure repeatedly.
ABS/ASR 5A4-3
Contents of ASR Control
The ASR controls the engine torque to prevent wheel
spin of the drive wheel during sudden start/acceleration.
The ABS/ASR control unit calculates the engine control
speed (average of the drive wheel RH and LH speed)
and the vehicle speed (driven wheel speed) based on
the signal transmitted from each wheel speed sensor.
When the drive wheel spins and the speed difference
between the engine control speed and the vehicle speed
reaches the specified value, the ABS/ASR control unit
send a signal to the engine control unit to operate the
throttle closing direction to adjust the slip amount appro-
priately.
2WD ABS
Legend
1. LSPV
2. Speed sensor (rear wheel)
3. Electronic hydraulic control unit (EHCU)
4. Battery
5. Speed sensor (front wheel)
6. Engine control unit
7. ABS warning lamp
8. Self-diagnosis connector
9. Brake switch
N5A2001E
5A4-4 ABS/ASR
ABS/ASR
Legend
1. LSPV
2. Speed sensor (rear wheel)
3. Electronic hydraulic control unit (EHCU)
4. Battery
5. Speed sensor (front wheel)
6. ASR OFF switch
7. Engine control unit
8. ASR warning lamp
9. ABS warning lamp
10. Self-diagnosis connector
11. Brake switch
Symptom Specific to the Model with ABS
The vehicle equipped with ABS may develop the follow-
ing symptoms, but those are inherent to the system and
not malfunction.
1. Kickback or vibration in the break pedal, vibration
in the steering wheel and vehicle are felt during
abrupt braking or braking on a slippery surface.
2. Noise is generated around the brake pedal or from
the vehicle rearward while ABS is in operation.
3. Motor operation noise is generated for short time
immediately after engine starting.
Abbreviation
Abbreviations are used in this section. Followings are
list of abbreviations for your convenience.
ABS
Anti-lock brake system
N5A2002E
ABS/ASR 5A4-5
ASR
Anti-slip regulator
CKT
Circuit
DLC
Data link connector
DTC
Diagnostic trouble code
ECM
Engine control module
ECU
Electronic control unit
EHCU
Electronic hydraulic control unit
FL
Front left
FR
Front right
GEN
Generator
HU
Hydraulic unit
LSPV
Load sensing proportioning valve
MV
Millivolt
RR
Rear right
RPS
Revolution per second
VDC
Volts, direct current
VAC
Volts, alternating current
VIM
Vehicle interface module
W/L
Warning light
WSS
Wheel speed sensor
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст