2004 INFINITI QX56 4WD

TROUBLE DIAGNOSES FOR SYMPTOMS
TF-89
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Revision: August 20072004 QX56
Symptom 4. ATP Warning Lamp Does Not Turn ON (When 4WD shift switch is
set from 4H to 4LO with the A/T selector lever in P position, the ATP warning
lamp does not turn on)
EDS0018H
1. CHECK ATP SWITCH CIRCUIT
Check ATP switch circuit.
Refer to TF-69, "
ATP SWITCH, WAIT DETECTION SWITCH AND
NEUTRAL-4LO SWITCH" .
OK or NG
OK >> GO TO 2.
NG >> Check, repair or replace faulty parts.
2. CHECK COMBINATION METER
Check the combination meter. Refer to DI-17, "
How to Proceed With Trouble Diagnosis"
OK or NG
OK >> Replace transfer control unit. Refer to TF-98, "Removal and Installation" .
NG >> Replace combination meter. Refer to DI-25, "
Removal and Installation of Combination Meter" .
WDIA0103E

TF-90
TROUBLE DIAGNOSES FOR SYMPTOMS
Revision: August 20072004 QX56
Symptom 5. 4LO Indicator Lamp Does Not Turn ON (When 4WD shift switch is
set from 4H to 4LO position, 4LO indicator lamp does not turn ON)
EDS0018I
1. CHECK TRANSFER CONTROL UNIT POWER SUPPLY CIRCUIT
1. Disconnect battery negative terminal, then transfer control unit connectors.
2. Connect battery negative terminal and turn ignition switch ON (with engine stopped).
3. Check voltage across transfer control unit connector E142 and E143 terminals 16 (Y/R), 47 (W) and
ground.
OK or NG
OK >> GO TO 2.
NG >> Check the following.

Continuity between battery, ignition switch and trans-
fer control unit

Ignition switch. Refer to PG-4, "POWER SUPPLY
ROUTING CIRCUIT" .

No. 53 fuse (20A) and No. 49 fuse (10A)
2. CHECK TRANSFER CONTROL UNIT GROUND CIRCUIT
1. Turn ignition switch to OFF position.
2. Disconnect transfer control unit harness connectors E142 and
E143.
3. Measure resistance between transfer control unit harness con-
nectors E142 and E143 terminals 3 (B), 6 (B), 45 (B) and
ground.
OK or NG
OK >> GO TO 3.
NG >> Check continuity between transfer control unit and
ground. Voltage : Battery voltage
WDIA0071E
WDIA0081E
Resistance : Continuity should exist.
LDIA0087E

TROUBLE DIAGNOSES FOR SYMPTOMS
TF-91
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Revision: August 20072004 QX56
3. CHECK 4LO INDICATOR LAMP CIRCUIT AND COMBINATION METER
Check the following.

Combination meter. Refer to DI-17, "How to Proceed With Trouble Diagnosis" .

Continuity between ignition switch and combination meter

Continuity between combination meter and transfer control unit

Condition of ATP and neutral-4LO switch circuit. Refer to TF-69, "ATP SWITCH, WAIT DETECTION
SWITCH AND NEUTRAL-4LO SWITCH" .
OK or NG
OK >> Replace transfer control unit. Refer to TF-98, "Removal and Installation" .
NG >>

Repair or replace harness or connector.

Replace combination meter. Refer to DI-25, "Removal and Installation of Combination Meter" .

Replace ATP or neutral-4LO switch.
Symptom 6. 4WD Shift Indicator Lamp Does Not Indicate “LOCK” (When 4WD
shift switch is set to “4H”, 4WD shift indicator lamp does not indicate “LOCK”)
EDS0018J
1. CHECK 4WD WARNING LAMP
Is 4WD warning lamp turned ON?
Ye s o r N o
Yes >> Refer to TF-27, "Trouble Diagnosis without CONSULT-
II" .
No >> GO TO 2.
2. CHECK NEUTRAL-4LO, WAIT DETECTION AND ATP SWITCH CIRCUITS
Check neutral-4LO, wait detection and ATP switch circuits. Refer to TF-69, "
ATP SWITCH, WAIT DETECTION
SWITCH AND NEUTRAL-4LO SWITCH" .
OK or NG
OK >> GO TO 3.
NG >> Check, repair or replace faulty parts.
3. CHECK PROCEDURES FROM THE BEGINNING AGAIN
Check again.
OK or NG
OK >> Inspection End.
NG >> Recheck each connector pin terminals for damage or loose connection.
WDIA0071E

TF-92
TROUBLE DIAGNOSES FOR SYMPTOMS
Revision: August 20072004 QX56
Symptom 7. 4WD Shift Indicator Lamp Repeats Flickering (4WD Shift Indicator
Lamp Keeps Flickering)
EDS0018K
1. CHECK 4WD SHIFT INDICATOR LAMP
1. Set 4WD shift switch to 2WD position.
2. Move vehicle forward and backward. Or drive straight increasing
or decreasing speed under 20 km/h (12 MPH).
3. Does 4WD shift indicator lamp keep flickering?
Ye s o r N o
Yes >> GO TO 2.
No >> Inspection End.
2. CHECK TIGHT CORNER BRAKING SYMPTOM
Drive vehicle at speed under 20 km/h (12 MPH), turning steering wheel to the limit. Does tight corner braking
symptom occur?
Ye s o r N o
Yes >> GO TO 3.
No >> GO TO 4.
3. CHECK 4WD SHIFT INDICATOR LAMP
Does the 4WD shift indicator lamp keep flickering when the front wheels are jacked up?
Ye s o r N o
Yes >> Check transfer unit operating system.
No >> Check tires.
4. CHECK 4WD WARNING LAMP
Does 4WD warning lamp flicker? (4WD shift indicator lamp is turned OFF.)
Ye s o r N o
Yes >> Perform self-diagnosis. Refer to TF-27, "Trouble Diagnosis without CONSULT-II" .
No >> GO TO 5.
5. CHECK 4WD SHIFT INDICATOR LAMP
Does 4WD shift indicator lamp keep flickering?
Ye s o r N o
Yes >> Check again.
No >> Inspection End.
WDIA0071E

TROUBLE DIAGNOSES FOR SYMPTOMS
TF-93
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Revision: August 20072004 QX56
Symptom 8. Tight Corner Braking Symptom (Tight Corner Braking Symptom
Occurs-Hydraulic System Failure)
EDS0018L
1. CHECK INPUT SIGNAL
With CONSULT-II
1. Select “ECU INPUT SIGNALS” in Data Monitor.
2. Put A/T selector lever in D.
3. Turn 4WD shift switch to 4H and back to 2WD while reading out
ON/OFF status of "CL PRES SW".
Without CONSULT-II
Check voltage between transfer control unit harness connector E143
terminal 34 (BR) and ground.
Refer to TF-55, "
TRANSFER CONTROL UNIT INSPECTION
TABLE" .
OK or NG
OK >> Disassemble transfer unit and check the following.

Control valve assembly

4WD solenoid valve

2-4WD shift solenoid valve

Clutch piston

Clutch assembly
NG >> GO TO 2.
2. CHECK CLUTCH PRESSURE SWITCH CIRCUIT
Check clutch pressure switch circuit.
Refer to TF-72, "
Diagnostic Procedure" .
OK or NG
OK >> GO TO 3.
NG >> Check, repair or replace faulty parts.
3. CHECK PROCEDURES FROM THE BEGINNING AGAIN
Check again.
OK or NG
OK >> Inspection End.
NG >> Recheck each connector pin terminals for damage or loose connection.
WDIA0087E

TF-94
TROUBLE DIAGNOSES FOR SYMPTOMS
Revision: August 20072004 QX56
Symptom 9. 4WD System Does Not Operate (The Vehicle Cannot Be Put Into
4WD Mode-Hydraulic System Failure)
EDS0018M
1. CHECK INPUT SIGNAL
With CONSULT-II
1. Select “ECU INPUT SIGNALS” in Data Monitor.
2. Put A/T selector lever in D.
3. Turn 4WD shift switch to 4H and back to 2WD while reading out
ON/OFF status of "CL PRES SW".
Without CONSULT-II
Check voltage between transfer control unit harness connector E143
terminal 34 (BR) and ground.
Refer to TF-55, "
TRANSFER CONTROL UNIT INSPECTION
TABLE" .
OK or NG
OK >> 1. Check transfer fluid level.
2. Disassemble transfer unit and check the following.
–Transfer motor
–Main oil pump assembly
–Sub-oil pump assembly
–Oil strainer
–Control valve assembly
–2-4WD shift solenoid valve
–Oil filter element
–Lip seal
–Strainer O-ring
–Main oil pump drive gear
–Seal ring
–D-ring
–Clutch piston
–Clutch assembly
NG >> GO TO 2.
2. CHECK CLUTCH PRESSURE CIRCUIT
Check clutch pressure switch circuit.
Refer to TF-72, "
Diagnostic Procedure" .
OK or NG
OK >> GO TO 3.
NG >> Check, repair or replace faulty parts.
3. CHECK PROCEDURES FROM THE BEGINNING
Check again.
OK or NG
OK >> Inspection End.
NG >> Recheck each connector pin terminals for damage or loose connection.
WDIA0087E

TROUBLE DIAGNOSES FOR SYMPTOMS
TF-95
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Revision: August 20072004 QX56
Component InspectionEDS0018N
4WD SHIFT SWITCH
Check continuity between each terminal.
2-4WD SHIFT SOLENOID VALVE AND TRANSFER FLUID TEMPERATURE SENSOR
Measure resistance between terminals of transfer terminal cord
assembly harness connector F56.
4WD SOLENOID VALVE, CLUTCH PRESSURE SWITCH AND LINE PRESSURE SWITCH
Measure resistance between terminals of transfer terminal cord
assembly harness connector F56.
Terminals Switch position Continuity
1 - 22WD Yes
Except 2WD No
1 - 3, 1 - 4AUTO Yes
Except AUTO No
1 - 4, 1 - 54H Yes
Except 4H No
1 - 4, 1 - 64LO Yes
Except 4LO No
WDIA0090E
Component parts TerminalsResistance
(Approx.)
2-4WD shift solenoid valve 4 - 520°C (68°F):
22.8 - 25.2Ω
Transfer fluid temperature
sensor2 - 320°C (68°F): 2.5 kΩ
80°C (176°F): 0.3 kΩ
LDIA0093E
Component
partsTerminals Remarks
4WD sole-
noid valve6
Ground
terminalApprox. 20°C (68°F): Approx. 3.0 - 3.4Ω
Clutch pres-
sure switch7In room temperature

2-4WD shift solenoid valve “OFF”: No conti-
nuity

2-4WD shift solenoid valve and transfer
motor “ON”: Continuity exists
Line pressure
switch1In room temperature

Turn ignition switch to “OFF” position and
leave vehicle for more than 5 minutes.
(OFF): No continuity

Transfer motor “ON”: Continuity exists
LDIA0094E

TF-98
TRANSFER CONTROL UNIT
Revision: August 20072004 QX56
TRANSFER CONTROL UNITPFP:33084
Removal and InstallationEDS00314
REMOVAL
1. Set transfer state as 2WD when 4WD shift switch is at 2WD, or as AUTO when 4WD shift switch is at
AUTO.
CAUTION:
When removing transfer control unit, transfer state must be at 2WD or AUTO.
2. Turn the ignition switch OFF and disconnect negative battery terminal.
3. Remove the glove box assembly. Refer to IP-14, "
Instrument Lower Cover RH and Glove Box" .
4. Disconnect the two transfer control unit connectors.
5. Remove the transfer control unit bolts.
6. Remove the transfer control unit.
INSTALLATION
Installation is in the reverse order of removal.

When installing the transfer control unit, tighten bolts to the specified torque.
CAUTION:

Do not connect harness connector to transfer control unit when 4WD shift switch is at 4LO.

After the installation, check perform self-diagnosis. Refer to TF-28, "SELF-DIAGNOSTIC PROCEDURE"
. If NG, adjust position between transfer assembly and transfer control unit.
BDIA0014E
Transfer control unit bolts : 5.1 N·m (0.52 kg-m, 45 in-lb)