2007 INFINITI QX56 low oil pressure

SERVICE DATA AND SPECIFICATIONS (SDS)
PS-27
< SERVICE INFORMATION >
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Oil PumpINFOID:0000000003532839
Steering FluidINFOID:0000000003532840
Rack sliding forceAt the neutral point:
Range within ± 11.5 mm
(±0.453 in) from the neutral
position
(in power ON)Area average value 147 − 211 N (14.99 − 21.52 kg, 33.1 − 47.52 lb)
Allowable variation 98 N (10 kg, 22 lb) or less
Whole area (in power OFF)Peak value 294 N (30.0 kg, 66 lb) or less
Allowable variation 147 N (16 kg, 35 lb) or less Steering gear modelPR26AM
Relief oil pressure
9.0 − 9.8 mPa (91.77 − 99.93 kg/cm2, 1305.34 − 1421.37 psi)
Fluid capacity
Approx. 1.0 (1-1/8 US qt, 7/8 Imp qt)

REAR SUSPENSION MEMBER
RSU-27
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Rear Load Leveling Air Suspension System
REMOVAL
1. Use the CONSULT-II “EXHAUST SOLENOID” active test to release the air pressure from the rear load
leveling air suspension system.
2. Disconnect the electrical connectors for the height sensor and the rear load leveling air suspension com-
pressor assembly.
3. Unclip the rubber cover to access the rear load leveling air suspension compressor assembly.
4. Disconnect the rear load leveling air suspension hoses at the
rear load leveling air suspension compressor assembly.
• To disconnect the hoses, push in on the lock ring using a suit-
able tool and pull the hose out.
5. Remove both of the rear wheel and tire assemblies using power
tool.
6. Remove the brake caliper without disconnecting the brake
hoses, using power tool. Reposition the brake caliper out of the
way using a suitable wire. Refer to BR-25, "
Removal and Instal-
lation of Brake Caliper and Disc Rotor" .
CAUTION:
10. Shock absorber 11. Suspension arm 12. Lower rubber seat
13. Coil spring 14. Upper rubber seat 15. Rear suspension member
16. Spare tire bracket 17. Bound bumper
AWEIA0076ZZ
1. Rear load leveling air suspension
hose, RH2. Shock absorber, RH 3. Height sensor
4. Rear load leveling air suspension
hose, LH5. Shock absorber, LH 6. Rear load leveling air suspension
compressor assembly (includes the
bracket and rubber cover)
⇐Front
LEIA0074E

REAR LOWER LINK & COIL SPRING
RSU-35
< SERVICE INFORMATION >
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REAR LOWER LINK & COIL SPRING
Removal and InstallationINFOID:0000000003532676
REMOVAL
1. Remove the wheel and tire assembly using power tool. Refer to WT-7, "Rotation" .
2. Use CONSULT-II "EXHAUST SOLENOID" active test to release the air pressure from the rear load level-
ing air suspension system.
3. For removing the LH rear lower link and coil spring, remove the
height sensor arm bracket bolt from the LH rear lower link.
4. Set a suitable jack to relieve the coil spring tension from the rear
lower link.
WARNING:
Do not compress the coil spring when setting the jack.
5. Loosen the rear lower link adjusting bolt and nut connected to
the rear suspension member, using power tool.
6. Remove the rear lower link bolt and nut from the knuckle using
power tool.
7. Slowly lower the suitable jack to release the coil spring tension. Then remove the upper rubber seat, coil
spring, and lower rubber seat from the rear lower link.
LEIA0080E
LEIA0077E
LEIA0009E
LEIA0077E

TF-16
< SERVICE INFORMATION >
ALL-MODE 4WD SYSTEM
Hydraulic Control Circuits
TRANSFER MOTOR
• The transfer motor drives the sub-oil pump to provide proper lubrication and oil pressure control when the
vehicle is at standstill, during low-speed operations or is being driven in reverse.
• The main oil pump is operated by the driving force of the mainshaft. In other words, sufficient oil pressure
buildup does not occur when the vehicle is at standstill or during low-speed operations. While the vehicle is
being driven in reverse, the main oil pump rotates in the reverse direction. Therefore the main oil pump does
not discharge oil pressure. During any of the above vehicle operations, the transfer motor drives the sub-oil
pump to compensate for insufficient oil pressure.
• The transfer motor operates as follows.
- The motor relay turns OFF in the 2WD mode.
- The motor relay operates as described in the table below in modes other than the 2WD mode.
Transfer Motor Relay Operation
LDIA0055E
WDIA0163E
4WD shift switch A/T selector lever positionVehicle speed
(VSS)Accelerator pedal positionMotor relay drive
command
2WD — — — OFF

ALL-MODE 4WD SYSTEM
TF-17
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*: After 2.5 seconds have elapsed.
• 4WD shift switch, PNP switch, Neutral-4LO switch, vehicle speed sensor and throttle position sensor are
used in conjunction with the transfer motor.
WAIT DETECTION SWITCH
• The wait detection switch operates when there is “circulating” torque produced in the propeller shaft (L→H)
or when there is a phase difference between 2-4 sleeve and clutch drum (H→L). After the release of the “cir-
culating” torque, the wait detection switch helps provide the 4WD lock gear (clutch drum) shifts. A difference
may occur between the operation of the 4WD shift switch and actual drive mode. At this point, the wait
detection switch senses an actual drive mode.
• The wait detection switch operates as follows.
- 4WD lock gear (clutch drum) locked: ON
- 4WD lock gear (clutch drum) released: OFF
• The wait detection switch senses an actual drive mode and the 4WD shift indicator lamp indicates the vehi-
cle drive mode.
NEUTRAL-4LO SWITCH
The neutral-4LO switch detects that transfer gear is in neutral or 4LO (or shifting from neutral to 4LO) condi-
tion by L-H shift fork position.
AT P S W I T C H
ATP switch detects if transfer gear is in a neutral condition by L-H shift fork position.
NOTE:
Transfer gear may be in a neutral condition in 4H-4LO.
2-4WD SHIFT SOLENOID VALVE
The 2-4WD shift solenoid valve operates to apply oil pressure to the wet-multiplate clutch, depending on the
drive mode. The driving force is transmitted to the front wheels through the clutch so the vehicle is set in the
4WD mode. Setting the vehicle in the 2WD mode requires no pressure buildup. In other words, pressure force
applied to the wet-multiplate clutch becomes zero.
CLUTCH PRESSURE SOLENOID VALVE
The clutch pressure solenoid valve distributes torque (front and rear) in AUTO mode.
4H (LOCK) and 4LO“N” position 0 — ON
“P” position 00 - 0.07/8 OFF*
0.07/8 - 1/8 HOLD
1/8 - MAX ON
Other than “R” position0 < VSS ≤ 50 km/h (31 MPH)
— ON
50 km/h (31 MPH) < VSS < 55
km/h (34 MPH) HOLD
55 km/h (34 MPH) ≤ VSS OFF
“R” position — — ON
“R” position — — ON
AUTO“P” or “N” position00 - 0.07/8 OFF*
0.07/8 - 1/8 HOLD
1/8 - MAX ON
0 < VSS ≤ 50 km/h (31 MPH)
— ON
50 km/h (31 MPH) < VSS < 55
km/h (34 MPH) HOLD
55 km/h (34 MPH) ≤ VSS OFF
Other than “R”, "P" and "N"
position0 < VSS ≤ 50 km/h (31 MPH)
— ON
50 km/h (31 MPH) < VSS < 55
km/h (34 MPH) HOLD
55 km/h (34 MPH) ≤ VSS OFF 4WD shift switch A/T selector lever positionVehicle speed
(VSS)Accelerator pedal positionMotor relay drive
command

TF-18
< SERVICE INFORMATION >
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-44
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
CAUTION:
• If “CAN COMM CIRCUIT [U1000]” is displayed with other DTCs, first perform the trouble diagnosis for CAN communication
line.
• If “VHCL SPEED SEN·AT [P1808]”, “ABS OP SIG [P1830]”, “VDC OP SIG [P1831]” or “TCS OP SIG [P1832]” is displayed, first
perform the trouble diagnosis for ABS system.
• If “VHCL SPEED SEN·AT [P1808]”, is displayed, first perform the trouble diagnosis for A/T system.
NOTE:
• If "SHIFT ACT POSI SW [P1818]" or “SHIFT ACT CIR [P1819]” is displayed, first erase self-diagnostic results. ("SHIFT ACT POSI SW
[P1818]" or “SHIFT ACT CIR [P1819]” may be displayed after installing transfer control unit or transfer assembly.)
• If “CL PRES SW [P1827]” or “LINE PRES SW [P1828]” is displayed only while driving in reverse, check the continuity of “R” position
on A/T PNP switch. When there is nothing wrong with the electrical system, check the hydraulic system.
How to Erase Self-diagnostic Results
1. Perform applicable inspection of malfunctioning item and then repair or replace.
SHIFT ACT CIR
[P1819]• Transfer control device actuator circuit is shorted or open. (Mal-
functions are detected when transfer shift relay circuit is open/
shorted or relay monitor circuit is open/shorted.)
• Malfunction occurs in transfer control device drive circuit.
• Malfunction is detected in transfer shut off relay.TF-72, "Transfer Control Device"
Malfunction is detected in transfer shut off relay.TF-51, "Power Supply Circuit for
Transfer Control Unit"
ENGINE SPEED SIG
[P1820]• Malfunction is detected in engine speed signal that is output from
ECM through CAN communication.
• Improper signal is input while driving.TF-76, "Engine Speed Signal
(ECM)"
DUTY SOLENOID
[P1822]• Proper voltage is not applied to clutch pressure solenoid valve
due to open or short circuit.TF-76, "Clutch Pressure Sole-
noid"
2-4WD SOLENOID
[P1823]• Proper voltage is not applied to 2-4WD solenoid valve due to open
or short circuit.TF-80, "2-4WD Solenoid"
MOTOR RELAY
[P1824]• Motor does not operate properly due to open or short circuit in
transfer motor or motor relay.TF-84, "Transfer Motor"
OIL TEMP SEN
[P1826]• Signal voltage from fluid temperature sensor is abnormally high
(Transfer fluid temperature is abnormally low) while driving.TF-90, "Transfer Fluid Tempera-
ture"
CLUTCH PRES SW
[P1827]• Improper signal from clutch pressure switch is input due to open or
short circuit.
• Malfunction occurs in clutch pressure switch or hydraulic circuit.TF-92, "Clutch Pressure Switch"
LINE PRES SW
[P1828]• Improper signal from line pressure switch is input due to open or
short circuit.
• Malfunction occurs in line pressure switch or hydraulic circuit.TF-94, "Line Pressure Switch"
THROTTLE POSI SEN
[P1829]• Malfunction is detected in accelerator pedal position signal that is
output from ECM through CAN communication.
• Signal voltage from accelerator pedal position sensor is abnormal-
ly high or low.TF-97, "Throttle Position Signal
(ECM)"
ABS OP SIG
[P1830]• Malfunction is detected in ABS operation signal that is output from
ABS actuator and electric unit (control unit) through CAN commu-
nication.TF-97, "ABS Operation Signal
(ABS)"
VDC OP SIG
[P1831]• Malfunction is detected in VDC operation signal that is output from
ABS actuator and electric unit (control unit) through CAN commu-
nication.TF-98, "VDC Operation Signal
(ABS)"
TCS OP SIG
[P1832]• Malfunction is detected in TCS operation signal that is output from
ABS through CAN communication.TF-98, "TCS Operation Signal
(ABS)"
CAN COMM CIRCUIT
[U1000]• Malfunction has been detected from CAN communication line.TF-99, "CAN Communication
Line"
NO DTC IS DETECTED.
FURTHER TESTING MAY
BE REQUIRED.• No NG item has been detected. — Items (CONSULT-II screen
terms)Diagnostic item is detected when... Check item