brake INFINITI QX4 2001 Factory Service Manual

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

Preliminary CheckNBBR0099
1 CHECK BRAKE FLUID
Check brake fluid for contamination.
Has brake fluid been contaminated?
Ye s©Replace. GO TO 2.
No©GO TO 2.
2 CHECK BRAKE FLUID LEVEL
Check brake fluid level in reservoir tank.
Low fluid level may indicate brake pad wear or leakage from brake line.
SBR451D
Is brake fluid filled between MAX and MIN lines on reservoir tank?
Ye s©GO TO 3.
No©Fill up brake fluid. GO TO 3.
3 CHECK BRAKE LINE
Check brake line for leakage.
SBR389C
Is leakage present at or around brake lines, tubes or hoses or are any of these parts cracked or damaged?
Ye s©Repair. GO TO 4.
No©GO TO 4.
TROUBLE DIAGNOSIS Ð BASIC INSPECTIONABS
Preliminary Check
BR-50

4 CHECK BRAKE BOOSTER OPERATION
Check brake booster for operation and air tightness.
Refer to ªOn-vehicle Serviceº, ªBRAKE BOOSTERº, BR-19.
SBR058C
Is brake booster airtight and functioning properly?
Ye s©GO TO 5.
No©Replace. GO TO 5.
5 CHECK BRAKE PAD AND ROTOR
Check brake pad and rotor.
Refer to (BR-22, BR-24).
SBR059C
Are brake pads and rotors functioning properly?
Ye s©GO TO 6.
No©Replace.
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TROUBLE DIAGNOSIS Ð BASIC INSPECTIONABS
Preliminary Check (Cont'd)
BR-51

6 RECHECK BRAKE FLUID LEVEL
Check brake fluid level in reservoir tank again.
SBR451D
Is brake fluid filled between MAX and MIN lines on reservoir tank?
Ye s©GO TO 7.
No©Fill up brake fluid.
7 CHECK WARNING LAMP ACTIVATION
Check warning lamp activation.
SBR672E
Does warning lamp turn on when ignition switch is turned ON?
Ye s©GO TO 8.
No©Check fuse, warning lamp bulb and warning lamp circuit.
8 CHECK WARNING LAMP DEACTIVATION
Check warning lamp for deactivation after engine is started.
Does warning lamp turn off when engine is started?
Ye s©GO TO 9.
No©Go to Self-diagnosis (BR-41, 44).
9 DRIVE VEHICLE
Drive vehicle at speeds over 30 km/h (19 MPH) for at least one minute.
Does warning lamp remain off after vehicle has been driven at 30 km/h (19 MPH) for at least one minute?
Ye s©INSPECTION END
No©Go to Self-diagnosis (BR-41, 44).
TROUBLE DIAGNOSIS Ð BASIC INSPECTIONABS
Preliminary Check (Cont'd)
BR-52

1. ABS Works FrequentlyNBBR0107
1 CHECK BRAKE FLUID PRESSURE
Check brake fluid pressure distribution.
Refer to ªInspectionº, ªLOAD SENSING VALVEº, BR-12.
Is brake fluid pressure distribution normal?
Ye s©GO TO 2.
No©Repair. Then perform Preliminary Check.
Refer to BR-50.
2 CHECK WHEEL SENSOR
1. Check wheel sensor connector for terminal damage or loose connections.
2. Perform wheel sensor mechanical check.
Refer to ª7. CHECK SENSOR ROTORº in ªDIAGNOSTIC PROCEDUREº, ªWheel Sensor or Rotorº, BR-56.
Is wheel sensor mechanism OK?
Ye s©GO TO 3.
No©Repair.
3 CHECK FRONT AXLE
Check front axles for excessive looseness. Refer to AX-4, ªFront Wheel Bearingº.
Is front axle installed properly?
Ye s©Go to ª3. CHECK WARNING LAMP INDICATIONº in ª2. Unexpected Pedal Actionº,
BR-70.
No©Repair.
2. Unexpected Pedal ActionNBBR0108
1 CHECK BRAKE PEDAL STROKE
Check brake pedal stroke.
SBR540A
Is brake pedal stroke excessively large?
Ye s©Perform Preliminary Check. Refer to BR-50.
No©GO TO 2.
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TROUBLE DIAGNOSES FOR SYMPTOMSABS
1. ABS Works Frequently
BR-69

2 CHECK MECHANICAL BRAKE SYSTEM PERFORMANCE
Disconnect ABS actuator and electric unit connector and check whether brake is effective.
Does brake system function properly when brake pedal is depressed?
Ye s©GO TO 3.
No©Perform Preliminary Check. Refer to BR-50.
3 CHECK WARNING LAMP INDICATION
Ensure warning lamp remains off while driving.
SBR672E
Is warning lamp turned off?
Ye s©GO TO 4.
No©Carry out self-diagnosis. Refer to BR-41, BR-44.
4 CHECK WHEEL SENSOR
1. Check wheel sensor connector for terminal damage or loose connection.
2. Perform wheel sensor mechanical check. Refer to ª7. CHECK SENSOR ROTORº in ªDIAGNOSTIC PROCEDUREº,
ªWheel Sensor or Rotorº, BR-56.
Is wheel sensor mechanism OK?
Ye s©Check ABS actuator and electric unit pin terminals for damage or the connection of ABS
actuator and electric unit harness connector.
Reconnect ABS actuator and electric unit harness connector.
Then retest.
No©Repair.
3. Long Stopping DistanceNBBR0109
1 CHECK MECHANICAL BRAKE SYSTEM PERFORMANCE
Disconnect ABS actuator and electric unit connector and check whether stopping distance is still long.
Does brake system function properly when brake pedal is depressed?
Ye s©Perform Preliminary Check and air bleeding (if necessary).
No©Go to ª3. CHECK WARNING LAMP INDICATIONº in ª2. Unexpected Pedal Actionº,
BR-70.
TROUBLE DIAGNOSES FOR SYMPTOMSABS
2. Unexpected Pedal Action (Cont'd)
BR-70

2 CHECK SYMPTOM
1. Apply brake.
2. Start engine.
Does the symptom appear only when engine is started?
Ye s©Carry out self-diagnosis. Refer to BR-41, 44.
No©Go to ª3. CHECK WARNING LAMP INDICATIONº in ª2. Unexpected Pedal Actionº,
BR-70.
NOTE:
ABS may operate and cause vibration under any of the following
conditions.
IApplying brake gradually when shifting or operating clutch.
ILow friction (slippery) road.
IHigh speed cornering.
IDriving over bumps and pot holes.
IEngine speed is over 5,000 rpm with vehicle stopped.
6. Warning Lamp Does Not Come On When
Ignition Switch Is Turned On
NBBR0112
1 INSPECTION START
Warning lamp circuit inspection
SBR673E
©GO TO 2.
2 CHECK FUSE
Check 10A fuse No. 8. For fuse layout, refer to EL-16, ªPOWER SUPPLY ROUTINGº.
Is fuse OK?
Ye s©GO TO 3.
No©Replace fuse.
TROUBLE DIAGNOSES FOR SYMPTOMSABS
5. Pedal Vibration and Noise (Cont'd)
BR-72

8. Vehicle Vibrates Excessively When ABS Is
Operating
=NBBR0078IWhile ABS is operating, brake pedal vibrates slightly. This is
not a problem.
IIf vehicle vibration is greater in the AUTO mode than in the
2WD mode, there is the possibility of failure in the communi-
cation line between the ABS control unit and transfer control
unit. Check and locate the cause of the problem.
1 INSPECTION START
Inspection for excessive vibration of vehicle
SBR508E
©GO TO 2.
2 CARRY OUT SELF-DIAGNOSIS
Perform self-diagnosis for the ABS actuator and electric unit and transfer control unit.
Are there any malfunctions?
Ye s©GO TO 3.
No©GO TO 4.
3 INSPECTION OR REPAIR
Inspect or repair the system according to the self-diagnostic item.
OK©GO TO 4.
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TROUBLE DIAGNOSES FOR SYMPTOMSABS
8. Vehicle Vibrates Excessively When ABS Is Operating
BR-77

ABS Actuator and Electric UnitNBBR0079S07
SBR468E
REMOVALNBBR0079S07011. Disconnect battery cable.
2. Drain brake fluid. Refer to ªChanging Brake Fluidº, BR-7.
3. Remove mounting bracket fixing bolts and nuts.
4. Disconnect connector, brake pipes and remove fixing nuts and
actuator ground cable.
INSTALLATIONNBBR0079S0702CAUTION:
After installation, refill brake fluid. Then bleed air. Refer to
ªBleeding Brake Systemº, BR-8.
1. Tighten actuator ground cable.
Place ground cable at a notch of mounting bracket.
2. Connect brake pipes temporarily.
3. Tighten fixing bolts and nuts.
4. Tighten brake pipes.
5. Connect connector and battery cable.
REMOVAL AND INSTALLATIONABS
ABS Actuator and Electric Unit
BR-82

General SpecificationsNBBR0118Unit: mm (in)
Applied model2WD 4WD
Front brakeBrake model AD31VC
Cylinder bore diameter´number of pistons 44.45 (1.7500)´2
Pad
Length´width´thickness132.0´52.5´11
(5.20´2.067´0.43)
Rotor outer diameter´thickness 300´28 (11.81´1.10)
Rear brakeBrake model LT30C
Cylinder bore diameter 22.23 (7/8)
Lining length´width´thickness296´50´6.1
(11.65´1.97´0.240)
Drum inner diameter 295.0 (11.61)
Master cylinder Bore diameter 25.40 (1)
Control valveValve modelProportioning valve
within master cylinderLinkage type load
sensing valve
Split point
kPa (kg/cm
2, psi)´reducing ratio2,942 (30, 427)´0.2 (Variable)´0.18
Brake boosterBooster model M235T
Diaphragm diameterPri: 252 (9.92)
Sec: 205 (8.07)
Recommended brake fluidDOT 3
Disc BrakeNBBR0119Unit: mm (in)
Brake modelAD31VC
Pad wear limit Minimum thickness 2.0 (0.079)
Rotor repair limit Minimum thickness 26.0 (1.024)
Drum BrakeNBBR0120Unit: mm (in)
Brake modelLT30C
Lining wear limit Minimum thickness 1.5 (0.059)
Drum repair limitMaximum inner diameter 296.5 (11.67)
Out-of-round limit 0.03 (0.0012)
Brake PedalNBBR0121Unit: mm (in)
TransmissionA/T
Free height ªHº*175 - 185
(6.89 - 7.28)
Depressed height ªDº*
[under force of 490 N (50 kg, 110 lb) with engine running]70 (2.76)
Clearance ªCº between pedal stopper and threaded end of stop lamp switch or ASCD switch 0.3 - 1.0 (0.012 - 0.039)
Pedal free playAt clevis 1.0 - 3.0 (0.039 - 0.118)
At pedal pad1 - 3 (0.04 - 0.12)
*: Measured from surface of metal panel to pedal pad
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SERVICE DATA AND SPECIFICATIONS (SDS)
General Specifications
BR-83