Infiniti QX4 (R50). Manual — part 109
SEF233G
SEF234G
How to Perform Trouble Diagnoses for Quick
and Accurate Repair
NBBR0098
INTRODUCTION
NBBR0098S01
The 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 “conventional” 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.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
ST
RS
BT
HA
SC
EL
IDX
TROUBLE DIAGNOSIS — INTRODUCTION
ABS
How to Perform Trouble Diagnoses for Quick and Accurate Repair
BR-49
Preliminary Check
NBBR0099
1
CHECK BRAKE FLUID
Check brake fluid for contamination.
Has brake fluid been contaminated?
Yes
©
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?
Yes
©
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?
Yes
©
Repair. GO TO 4.
No
©
GO TO 4.
TROUBLE DIAGNOSIS — BASIC INSPECTION
ABS
Preliminary Check
BR-50
4
CHECK BRAKE BOOSTER OPERATION
Check brake booster for operation and air tightness.
Refer to “On-vehicle Service”, “BRAKE BOOSTER”, BR-19.
SBR058C
Is brake booster airtight and functioning properly?
Yes
©
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?
Yes
©
GO TO 6.
No
©
Replace.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
ST
RS
BT
HA
SC
EL
IDX
TROUBLE DIAGNOSIS — BASIC INSPECTION
ABS
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?
Yes
©
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?
Yes
©
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?
Yes
©
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?
Yes
©
INSPECTION END
No
©
Go to Self-diagnosis (BR-41, 44).
TROUBLE DIAGNOSIS — BASIC INSPECTION
ABS
Preliminary Check (Cont’d)
BR-52
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