Infiniti QX4 (R50). Manual — part 105
System Components
NBBR0090
SBR447EB
SBR124B
System Description
NBBR0091
SENSOR
NBBR0091S01
The 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)
NBBR0091S02
The 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 UNIT
NBBR0091S03
The ABS actuator and electric unit contains:
I
An electric motor and pump
I
Two relays
I
Six solenoid valves, each inlet and outlet for
— LH front
— RH front
— Rear
I
ABS control unit
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
ST
RS
BT
HA
SC
EL
IDX
DESCRIPTION
ABS
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 Operation
NBBR0091S0301
Inlet solenoid
valve
Outlet 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 operation
Pressure hold
ON (Closed)
OFF (Closed)
Hydraulic circuit is shut off to hold the caliper
brake fluid pressure.
Pressure
decrease
ON (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)
NBBR0091S05
The G sensor senses deceleration during braking to determine
whether the vehicle is being driven on a high µ road (asphalt road,
etc.) or a low µ 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 µ 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.
DESCRIPTION
ABS
System Description (Cont’d)
BR-34
Component Parts and Harness Connector
Location
NBBR0092
SBR669E
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
ST
RS
BT
HA
SC
EL
IDX
DESCRIPTION
ABS
Component Parts and Harness Connector Location
BR-35
Schematic
NBBR0093
MBR436A
DESCRIPTION
ABS
Schematic
BR-36
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