2007 INFINITI QX56 service

TF-18
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ALL-MODE 4WD SYSTEM
LINE PRESSURE SWITCH
• With the transfer system design, control of the oil pressure provides the transmission of drive torque to the
front wheels. The main pressure to control the oil pressure is referred to as the line pressure.
• The line pressure switch determines whether or not adequate line pressure has built up under different oper-
ating conditions.
• The line pressure switch turns ON when line pressure is produced.
• The line pressure switch senses line pressure abnormalities and turns the 4WD warning lamp ON.
CLUTCH PRESSURE SWITCH
• The clutch pressure switch determines whether or not adequate clutch pressure has built up under different
operating conditions.
• The clutch pressure switch turns ON when clutch pressure is produced.
• The clutch pressure switch senses clutch pressure abnormalities and turns the 4WD warning lamp ON.
TRANSFER FLUID TEMPERATURE SENSOR
The transfer temperature sensor detects the transfer fluid temperature and sends a signal to the transfer con-
trol unit.
TRANSFER CONTROL UNIT
• Transfer control unit controls transfer control device by input signals of each sensor and each switch.
• Self-diagnosis can be done.
TRANSFER CONTROL DEVICE
The transfer control device changes the state of transfer assembly between 2WD, AUTO, 4H⇔4LO with the
2WD, AUTO, 4H and 4LO signals of 4WD shift switch.
NOTE:
• To shift between 4H⇔4LO, stop the vehicle, depress the brake pedal and shift the transmission selector to
the "N" position. Depress and turn the 4WD shift switch. The shift switch will not shift to the desired mode if
the transmission is not in "N" or the vehicle is moving. The 4LO indicator lamp will be lit when the 4LO is
engaged.
• Actuator motor and actuator position switch are integrated.
4WD SHIFT SWITCH AND INDICATOR LAMP
4WD Shift Switch
The 4WD shift switch allows selection from 2WD, AUTO, 4H or 4LO.
4WD Shift Indicator Lamp
• Displays driving conditions selected by 4WD shift switch with 2WD, AUTO and 4H indicators while engine is
running. (When 4WD warning lamp is turned on, all 4WD shift indicator lamps are turned off.)
• Turns ON for approximately 1 second when ignition switch is turned ON, for purpose of lamp check.
4LO Indicator Lamp
• Displays 4LO condition while engine is running. 4LO indicator lamp flashes if transfer gear does not shift
completely under 2WD, AUTO, 4H⇔4LO. (When 4WD warning lamp is turned on, 4LO indicator lamp is
turned off.)
• Turns ON for approximately 1 second when ignition switch is turned ON, for purpose of lamp check.
4WD WARNING LAMP
Turns ON or FLASH when there is a malfunction in 4WD system.
Also turns ON when ignition switch is turned ON, for purpose of lamp check. Turns OFF for approximately 1
second after the engine starts if system is normal.
4WD Warning Lamp Indication
Condition Content 4WD warning lamp
During self-diagnosis Indicates the malfunction position by number of flickers. Flickers at malfunction mode.
Lamp check*Checks the lamp by turning ON during engine starting. After
engine starts, it turns OFF if there are no malfunctions.ON
Malfunction in 4WD system*Turns ON to indicate malfunction. When ignition switch is
turned to “OFF” or the malfunction is corrected, it turns OFF.ON
When vehicle is driven with different
diameters of front and rear tiresFlickers once every 2 seconds.
Turns OFF when ignition switch is “OFF”.Flickers once every 2 sec-
onds.

ALL-MODE 4WD SYSTEM
TF-19
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*: When 4WD warning lamp is ON, all the 4WD shift indicator lamps turn OFF.
ATP WARNING LAMP
Even if A/T selector lever is in “P” position, vehicle may move because A/T parking mechanism does not oper-
ate when transfer is under neutral condition. ATP warning lamp is turned on so as to indicate this condition to
the driver.
SchematicINFOID:0000000003532518
COMPONENTS FUNCTION
High fluid temperature in transfer unitWhen fluid temperature is high or fluid temperature sensor cir-
cuit is shorted, it flickers twice every second.
It turns OFF when fluid temperature becomes normal.Flickers twice a second.
Other than above (System is normal.) Lamp is OFF. OFFCondition Content 4WD warning lamp
WDIA0164E
Component parts Function
Transfer control unit Controls transfer control device and control valves.
Transfer control device Actuator motor and actuator position switch are integrated so as to switch driving types.
2-4WD shift solenoid valve Controls oil pressure and allows selection between 2WD and 4WD.
Clutch pressure solenoid valve Controls oil pressure and distributes torque (front and rear).
Line pressure switch Detects line pressure.
Clutch pressure switch Detects clutch pressure.
Transfer fluid temperature sen-
sorDetects transfer fluid temperature.
Wait detection switch Detects whether or not 4WD lock gear is locked.
Neutral-4LO switch Detects that transfer is under neutral-4LO condition (or shifting through neutral).
ATP switch Detects that transfer is under neutral condition.
4WD shift switch Allows selection from 2WD, AUTO, 4H or 4LO.
4WD warning lamp• Illuminates if malfunction is detected in electrical system of 4WD system.
• There is 1 blink every 2 seconds if rotation difference of front wheels and rear wheels is large.
• There is 2 blinks every 1 second if high transfer fluid temperature is detected.
AT P w a r n i n g l a m pIndicates that A/T parking mechanism does not operate when A/T selector lever is in “P” position and
transfer is under neutral condition.
4WD shift indicator lamp Displays driving condition selected by 4WD shift switch.
4LO indicator lamp Displays 4LO condition.

TF-20
< SERVICE INFORMATION >
ALL-MODE 4WD SYSTEM
CAN Communication
INFOID:0000000003532519
SYSTEM DESCRIPTION
Refer to LAN-4.
ABS actuator and electric unit
(control unit)Transmits vehicle speed signal via CAN communication to transfer control unit.
TCMTransmits the following signals via CAN communication to transfer control unit.
• Output shaft revolution signal
• A/T position indicator signal (PNP switch signal)
ECMTransmits the following signals via CAN communication to transfer control unit.
• Engine speed signal
• Accelerator pedal position signal Component parts Function

TROUBLE DIAGNOSIS
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TROUBLE DIAGNOSIS
How to Perform Trouble DiagnosisINFOID:0000000003532520
BASIC CONCEPT
• To perform trouble diagnosis, it is the most important to have understanding about vehicle systems (control
and mechanism) thoroughly.
• It is also important to clarify customer complaints before inspec-
tion.
First of all, reproduce symptoms, and understand them fully.
Ask customer about his/her complaints carefully. In some cases, it
will be necessary to check symptoms by driving vehicle with cus-
tomer.
CAUTION:
Customers are not professional. It is dangerous to make an
easy guess like "maybe the customer means that...," or
"maybe the customer mentions this symptom".
• It is essential to check symptoms right from the beginning in order
to repair malfunctions completely.
For intermittent malfunctions, reproduce symptoms based on inter-
view with customer and past examples. Do not perform inspection
on ad hoc basis. Most intermittent malfunctions are caused by
poor contacts. In this case, it will be effective to shake suspected
harness or connector by hand. When repairing without any symp-
tom diagnosis, you cannot judge if malfunctions have actually been
eliminated.
• After completing diagnosis, always erase diagnostic memory.
Refer to TF-48, "
Self-Diagnosis Procedure" .
• For intermittent malfunctions, move harness or harness connector
by hand. Then check for poor contact or reproduced open circuit.
SEF233G
SEF234G

TF-22
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TROUBLE DIAGNOSIS
Location of Electrical Parts
INFOID:0000000003532521
WDIA0220E

TROUBLE DIAGNOSIS
TF-23
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Circuit DiagramINFOID:0000000003532522
BDWA0101E

TF-24
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TROUBLE DIAGNOSIS
Wiring Diagram - T/F -
INFOID:0000000003532523
BDWA0166E

TROUBLE DIAGNOSIS
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BDWA0167E