INFINITI QX4 2001 Factory Service Manual

PurposeNBBR0087The Anti-Lock Brake System (ABS) consists of electronic and hydraulic components. It allows for control of
braking force so locking of the wheels can be avoided.
1) Improves proper tracking performance through steering wheel operation.
2) Eases obstacle avoidance through steering wheel operation.
3) Improves vehicle stability.
OperationNBBR0088IWhen the vehicle speed is less than 10 km/h (6 MPH) this system does not work.
IThe Anti-Lock Brake System (ABS) has a self-test function. The system turns on the ABS warning lamp
for 1 second each time the ignition switch is turned ªONº. After the engine is started, the ABS warning lamp
turns off. The system performs a test the first time the vehicle reaches 6 km/h (4 MPH). A mechanical noise
may be heard as the ABS performs this self-test. This is a normal part of the self-test feature. If a mal-
function is found during this check, the ABS warning lamp will stay on.
IWhile driving, a mechanical noise may be heard during ABS operation. This is a normal condition.
ABS Hydraulic CircuitNBBR0089
SBR859D
1. Inlet solenoid valve
2. Outlet solenoid valve
3. Reservoir4. Pump
5. Motor
6. Inlet valve7. Outlet valve
8. Bypass check valve
9. Damper
DESCRIPTIONABS
Purpose
BR-32

System ComponentsNBBR0090
SBR447EB
SBR124B
System DescriptionNBBR0091SENSORNBBR0091S01The sensor unit consists of a gear-shaped sensor rotor and a sen-
sor element. The element contains a bar magnet around which a
coil is wound. The front sensors are installed on the front spindles
and the rear sensors are installed on the rear spindles. As the
wheel rotates, the sensor generates a sine-wave pattern. The fre-
quency and voltage increase(s) as the rotating speed increases.
SBR668E
CONTROL UNIT (BUILT-IN ABS ACTUATOR AND
ELECTRIC UNIT)
NBBR0091S02The control unit computes the wheel rotating speed by the signal
current sent from the sensor. Then it supplies a DC current to the
actuator solenoid valve. It also controls ON-OFF operation of the
valve relay and motor relay. If any electrical malfunction should be
detected in the system, the control unit causes the warning lamp
to light up. In this condition, the ABS will be deactivated by the
control unit, and the vehicle's brake system reverts to normal
operation. (For control unit layout, refer to ABS ACTUATOR AND
ELECTRIC UNIT, BR-33.)
SBR482E
ABS ACTUATOR AND ELECTRIC UNITNBBR0091S03The ABS actuator and electric unit contains:
IAn electric motor and pump
ITwo relays
ISix solenoid valves, each inlet and outlet for
Ð LH front
Ð RH front
Ð Rear
IABS control unit
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DESCRIPTIONABS
System Components
BR-33

This component controls the hydraulic circuit and increases, holds
or decreases hydraulic pressure to all or individual wheels. The
ABS actuator and electric unit is serviced as an assembly.
ABS Actuator OperationNBBR0091S0301
Inlet solenoid
valveOutlet solenoid
valve
Normal brake operation OFF (Open) OFF (Closed)Master cylinder brake fluid pressure is directly
transmitted to caliper via the inlet solenoid valve.
ABS operationPressure hold ON (Closed) OFF (Closed)Hydraulic circuit is shut off to hold the caliper
brake fluid pressure.
Pressure
decreaseON (Closed) ON (Open)Caliper brake fluid is sent to reservoir via the out-
let solenoid valve. Then it is pushed up to the
master cylinder by pump.
Pressure increase OFF (Open) OFF (Closed)Master cylinder brake fluid pressure is transmitted
to caliper.
G SENSOR (4WD MODELS ONLY)NBBR0091S05The G sensor senses deceleration during braking to determine
whether the vehicle is being driven on a high  road (asphalt road,
etc.) or a low  road (snow-covered road, etc.). It then sends a
signal to the ABS control unit.
SBR456E
The reed switch turns on when it is affected by a magnetic field.
During sudden deceleration (braking on a high  road), the weight
moves and the magnet in the weight moves away from the reed
switch. The magnetic field then diminishes and the reed switch
turns off.
DESCRIPTIONABS
System Description (Cont'd)
BR-34

Component Parts and Harness Connector
Location
NBBR0092
SBR669E
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DESCRIPTIONABS
Component Parts and Harness Connector Location
BR-35

SchematicNBBR0093
MBR436A
DESCRIPTIONABS
Schematic
BR-36

Wiring Diagram Ð ABS ÐNBBR0094
MBR437A
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DESCRIPTIONABS
Wiring Diagram Ð ABS Ð
BR-37

MBR438A
DESCRIPTIONABS
Wiring Diagram Ð ABS Ð (Cont'd)
BR-38

MBR439A
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DESCRIPTIONABS
Wiring Diagram Ð ABS Ð (Cont'd)
BR-39

MBR440A
DESCRIPTIONABS
Wiring Diagram Ð ABS Ð (Cont'd)
BR-40

Self-diagnosisNBBR0095FUNCTIONNBBR0095S01IWhen a problem occurs in the ABS, the warning lamp on the
instrument panel comes on. To start the self-diagnostic results
mode, ground the self-diagnostic (check) terminal located on
data link connector. The location of the malfunction is indicated
by the warning lamp flashing.
SELF-DIAGNOSIS PROCEDURENBBR0095S021. Drive vehicle over 30 km/h (19 MPH) for at least one minute.
2. Turn ignition switch OFF.
SBR665E
3. Ground terminal 9 of data link connector with a suitable har-
ness.
4. Turn ignition switch ON while grounding terminal 9.
Do not depress brake pedal.
SBR668E
5. After 3.0 seconds, the warning lamp starts flashing to indicate
the malfunction code No. (See NOTE.)
6. Verify the location of the malfunction with the malfunction code
chart. Refer to BR-54. Then make the necessary repairs fol-
lowing the diagnostic procedures.
7. After the malfunctions are repaired, erase the malfunction
codes stored in the control unit. Refer to BR-42.
8. Rerun the self-diagnostic results mode to verify that the mal-
function codes have been erased.
9. Disconnect the check terminal from the ground. The self-diag-
nostic results mode is now complete.
10. Check warning lamp for deactivation after driving vehicle over
30 km/h (19 MPH) for at least one minute.
11. After making certain that warning lamp does not come on, test
the ABS in a safe area to verify that it functions properly.
NOTE:
The indication terminates after 5 minutes.
However, when the ignition switch is turned from OFF to ON, the
indication starts flashing again.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONABS
Self-diagnosis
BR-41