2001 INFINITI QX4 02 sensor

InspectionNBBR0014CAUTION:
ICarefully monitor brake fluid level at master cylinder.
IUse new brake fluid ªDOT 3º.
IBe careful not to splash brake fluid on painted areas; it
may cause paint damage. If brake fluid is splashed on
paint areas, wash it away with water immediately.
IDepress pedal slowly when raising front brake pressure.
ICheck rear brake pressure 2 seconds after front brake
pressure reaches specified value.
IDisconnect harness connectors from ABS actuator and
electric unit before checking.
SBR212E
1. Park vehicle on a level surface with vehicle unloaded*.
* Fuel, radiator coolant and engine oil full. Spare tire, jack,
hand tools and mats in designated positions.
2. Press a lever to the stopper bolt, then check length ªBº as fol-
lows:
Length ªBº Reference (Length ªLº)
207.7 mm (8.18 in) 217.3 mm (8.56 in)
3. If length ªBº is not within specification, adjust sensor spring
length.
Removal and InstallationNBBR0015CAUTION:
IRefill with new brake fluid ªDOT 3º.
IBe careful not to splash brake fluid on painted areas; it
may cause paint damage. If brake fluid is splashed on
painted areas, wash it away with water immediately.
IDo not reuse Load Sensing Valve once it is disassembled.
IReplace damaged Load Sensing Valve as an assembly.
IWhen disassembling, apply multi-purpose grease to all
rubbing areas.
LOAD SENSING VALVE (4WD)
Inspection
BR-12

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

CONSULT-II=NBBR0096CONSULT-II APPLICATION TO ABSNBBR0096S01
ITEMSELF-DIAGNOSTIC
RESULTSDATA MONITOR ACTIVE TEST
Front right wheel sensor´´Ð
Front left wheel sensor´´Ð
Rear right wheel sensor´´Ð
Rear left wheel sensor´´Ð
G switch (G sensor)H´´´
ABS sensor´ÐÐ
Stop lamp switch дÐ
Front right inlet solenoid valve´´´
Front right outlet solenoid valve´´´
Front left inlet solenoid valve´´´
Front left outlet solenoid valve´´´
Rear inlet solenoid valve´´´
Rear outlet solenoid valve´´´
Actuator solenoid valve relay´´Ð
Actuator motor relay
(ABS MOTOR is shown on the Data Monitor
screen.)´´´
ABS warning lamp дÐ
Battery voltage´´Ð
Control unit´ÐÐ
ABS operating signal д´
´: Applicable
Ð: Not applicable
H: 4WD models only
ECU (ABS CONTROL UNIT) PART NUMBER MODENBBR0096S02Ignore the ECU part number displayed in the ECU PART NUMBER MODE. Refer to parts catalog to order
the ECU.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONABS
CONSULT-II
BR-43

SELF-DIAGNOSTIC RESULTS MODENBBR0097S02
Diagnostic item Diagnostic item is detected when ... Reference Page
FR RH SENSOR*1
[OPEN]ICircuit for front right wheel sensor is open.
(An abnormally high input voltage is entered.)BR-56
FR LH SENSOR*1
[OPEN]ICircuit for front left wheel sensor is open.
(An abnormally high input voltage is entered.)BR-56
RR RH SENSOR*1
[OPEN]ICircuit for rear right sensor is open.
(An abnormally high input voltage is entered.)BR-56
RR LH SENSOR*1
[OPEN]ICircuit for rear left sensor is open.
(An abnormally high input voltage is entered.)BR-56
FR RH SENSOR*1
[SHORT]ICircuit for front right wheel sensor is shorted.
(An abnormally low input voltage is entered.)BR-56
FR LH SENSOR*1
[SHORT]ICircuit for front left wheel sensor is shorted.
(An abnormally low input voltage is entered.)BR-56
RR RH SENSOR*1
[SHORT]ICircuit for rear right sensor is shorted.
(An abnormally low input voltage is entered.)BR-56
RR LH SENSOR*1
[SHORT]ICircuit for rear left sensor is shorted.
(An abnormally low input voltage is entered.)BR-56
ABS SENSOR*1
[ABNORMAL SIGNAL]ITeeth damage on sensor rotor or improper installation of wheel sensor.
(Abnormal wheel sensor signal is entered.)BR-56
FR RH IN ABS SOL
[OPEN, SHORT]ICircuit for front right inlet solenoid valve is open.
(An abnormally low output voltage is entered.)BR-59
FR LH IN ABS SOL
[OPEN, SHORT]ICircuit for front left inlet solenoid valve is open.
(An abnormally low output voltage is entered.)BR-59
FR RH OUT ABS SOL
[OPEN, SHORT]ICircuit for front right outlet solenoid valve is open.
(An abnormally low output voltage is entered.)BR-59
FR LH OUT ABS SOL
[OPEN, SHORT]ICircuit for front left outlet solenoid valve is open.
(An abnormally low output voltage is entered.)BR-59
RR IN ABS SOL
[OPEN, SHORT]ICircuit for rear inlet solenoid valve is shorted.
(An abnormally high output voltage is entered.)BR-59
RR OUT ABS SOL
[OPEN, SHORT]ICircuit for rear out solenoid valve is shorted.
(An abnormally high output voltage is entered.)BR-59
ABS ACTUATOR RELAY
[ABNORMAL]IActuator solenoid valve relay is ON, even if control unit sends off signal.
IActuator solenoid valve relay is OFF, even if control unit sends on signal.BR-59
ABS MOTOR RELAY
[ABNORMAL]ICircuit for ABS motor relay is open or shorted.
ICircuit for actuator motor is open or shorted.
IActuator motor relay is stuck.BR-61
BATTERY VOLT
[VB-LOW]IPower source voltage supplied to ABS control unit is abnormally low.
BR-63
CONTROL UNITIFunction of calculation in ABS control unit has failed. BR-68
G SENSOR*2
[ABNORMAL]IG sensor circuit is open or shorted.
BR-65
*1: If one or more wheels spin on a rough or slippery road for 40 seconds or more, the ABS warning lamp will illuminate. This does not
indicate a malfunction. Only in the case of the short-circuit (Code Nos. 26, 22, 32 and 36), after repair the ABS warning lamp also illu-
minates when the ignition switch is turned ON. In this case, drive the vehicle at speeds greater than 30 km/h (19 MPH) for approxi-
mately 1 minute as specified in ªSELF-DIAGNOSIS PROCEDUREº, BR-41. Check to ensure that the ABS warning lamp goes out while
the vehicle is being driven.
*2: 4WD models onlyGI
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONABS
CONSULT-II Inspection Procedure (Cont'd)
BR-45

DATA MONITOR MODENBBR0097S05
MONITOR ITEM CONDITION SPECIFICATION
FR RH SENSOR
FR LH SENSOR
RR RH SENSOR
RR LH SENSORDrive vehicle.
(Each wheel is rotating.)Wheel speed signal
(Almost the same speed as speedometer.)
STOP LAMP SW Brake is depressed.Depress the pedal: ON
Release the pedal: OFF
G-SWITCHHVehicle is driven.
Vehicle is stopped.
Brake is applied.During sudden braking while driving on high  roads (asphalt
roads, etc.): OFF
While vehicle is stopped or during constant-speed driving: ON
FR RH IN SOL
FR RH OUT SOL
FR LH IN SOL
FR LH OUT SOL
RR IN SOL
RR OUT SOL1. Drive vehicle at speeds
over 30 km/h (19 MPH) for at
least 1 minute.
2. Engine is running.Operating conditions for each solenoid valve are indicated. ABS
is not operating: OFF
MOTOR RELAYABS is not operating: OFF
ABS is operating: ON
ACTUATOR RELAY
Ignition switch is ON or
engine is running.Ignition switch ON (Engine stops): OFF
Engine running: ON
WARNING LAMPABS warning lamp is turned on: ON
ABS warning lamp is turned off: OFF
BATTERY VOLT Power supply voltage for control unit
ABS OPER SIGABS is not operating: OFF
ABS is operating: ON
H: 4WD model only
ACTIVE TEST MODENBBR0097S06
TEST ITEM CONDITION JUDGEMENT
FR RH SOLENOID
FR LH SOLENOID
RR SOLENOID
Engine is running.Brake fluid pressure control operation
IN SOL OUT SOL
UP (Increase): OFF OFF
KEEP (Hold): ON OFF
DOWN (Decrease): ON ON
ABS MOTORABS actuator motor
ON: Motor runs (ABS motor relay ON)
OFF: Motor stops (ABS motor relay OFF)
ABS OPER SIGIgnition switch is ON or
engine is running.ON: Set ABS OPER SIG ªONº (ABS is operating.)
OFF: Set ABS OPER SIG ªOFFº (ABS is not operating.)
G SWITCHHIgnition switch is ON.G SWITCH (G SENSOR)
ON: Set G SWITCH MONITOR ªONº (G switch circuit is
closed.)
OFF: Set G SWITCH MONITOR ªOFFº (G switch circuit is
open.)
H: 4WD models only
NOTE:
Active test will automatically stop ten seconds after the test starts. (TEST IS STOPPED monitor shows ON.)
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONABS
CONSULT-II Inspection Procedure (Cont'd)
BR-48

SEF233G
SEF234G
How to Perform Trouble Diagnoses for Quick
and Accurate Repair
NBBR0098INTRODUCTIONNBBR0098S01The ABS system has an electronic control unit to control major
functions. The control unit accepts input signals from sensors and
instantly drives the actuators. It is essential that both kinds of sig-
nals are proper and stable. It is also important to check for conven-
tional problems: such as air leaks in booster lines, lack of brake
fluid, or other problems with the brake system.
It is much more difficult to diagnose a problem that occurs intermit-
tently rather than continuously. Most intermittent problems are
caused by poor electric connections or faulty wiring. In this case,
careful checking of suspicious circuits may help prevent the
replacement of good parts.
A visual check only may not find the cause of the problems, so a
road test should be performed.
Before undertaking actual checks, take a few minutes to talk with
a customer who approaches with an ABS complaint. The customer
is a very good source of information on such problems; especially
intermittent ones. By talking to the customer, find out what symp-
toms are present and under what conditions they occur. Start your
diagnosis by looking for ªconventionalº problems first. This is one
of the best ways to troubleshoot brake problems on an ABS con-
trolled vehicle.
Also check related Service bulletins for information.
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TROUBLE DIAGNOSIS Ð INTRODUCTIONABS
How to Perform Trouble Diagnoses for Quick and Accurate Repair
BR-49

Malfunction Code/Symptom ChartNBBR0101
Code No. (No. of warning lamp flashes) Malfunctioning part Reference Page
12 Self-diagnosis could not detect any malfunctions. Ð
17*4 G sensor and circuit BR-65
18*1 Sensor rotor BR-56
21*1 Front right sensor (open-circuit) BR-56
22*1 Front right sensor (short-circuit) BR-56
25*1 Front left sensor (open-circuit) BR-56
26*1 Front left sensor (short-circuit) BR-56
31*1 Rear right sensor (open-circuit) BR-56
32*1 Rear right sensor (short-circuit) BR-56
35*1 Rear left sensor (open-circuit) BR-56
36*1 Rear left sensor (short-circuit) BR-56
41 Actuator front right outlet solenoid valve BR-59
42 Actuator front right inlet solenoid valve BR-59
45 Actuator front left outlet solenoid valve BR-59
46 Actuator front left inlet solenoid valve BR-59
55 Actuator rear outlet solenoid valve BR-59
56 Actuator rear inlet solenoid valve BR-59
57*2 Power supply (Low voltage) BR-63
61*3 Actuator motor or motor relay BR-61
63 Solenoid valve relay BR-59
71 Control unit BR-68
Warning lamp stays on when ignition
switch is turned ON.Control unit power supply circuit
Warning lamp bulb circuit
Control unit or control unit connector
Solenoid valve relay stuck
Power supply for solenoid valve relay coilBR-74
ABS works frequently Ð BR-69
Unexpected pedal action Ð BR-69
Long stopping distance Ð BR-70
ABS does not work Ð BR-71
Pedal vibration and noise Ð BR-71
Warning lamp does not come on
when ignition switch is turned ON.Fuse, warning lamp bulb or warning lamp circuit
Control unitBR-72
Vehicle vibrates excessively when ABS is
operating.ABS control unit to TCM circuit BR-77
*1: If one or more wheels spin on a rough or slippery road for 40 seconds or more, the ABS warning lamp will illuminate. This does not
indicate a malfunction. Only in the case of the short-circuit (Code Nos. 26, 22, 32 and 36), after repair the ABS warning lamp also illu-
minates when the ignition switch is turned ON. In this case, drive the vehicle at speeds greater than 30 km/h (19 MPH) for approxi-
mately 1 minute as specified in ªSELF-DIAGNOSIS PROCEDUREº, BR-41. Check to ensure that the ABS warning lamp goes out while
the vehicle is being driven.
*2: The trouble code ª57º, which refers to a low power supply voltage, does not indicate that the ABS control unit is malfunctioning. Do
not replace the ABS control unit with a new one.
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTIONABS
Malfunction Code/Symptom Chart
BR-54