2008 INFINITI QX56 oil pressure

DLN-14
< FUNCTION DIAGNOSIS >[ATX14B]
4WD SYSTEM
• 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 flashes when there is a malfunction in 4WD system.
Also turns on when ignition switch is turned ON, for purpose of lamp che\
ck. Turns OFF approximately 1 sec-
ond after the engine starts if system is normal.
4WD Warning Lamp Indication
ATP WARNING LAMP
When the A/T selector lever is in P position, the vehicle may move if the transfer case is in neutral. ATP warn-
ing lamp is turned on to indicate this condition to the driver.
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 closes 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 closes when clutch pressure is produced.
• The clutch pressure switch senses clutch pressure abnormalities and turns the 4WD warning lamp ON.
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 circu-
lating torque, the wait detection switch helps provi de the 4WD lock gear (clutch drum) shifts. A difference
may occur between the operation of the 4WD shift swit ch 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.
ATP SWITCH
ATP switch detects if transfer case is in neutral by the position of the L-H shift fork.
NOTE:
Transfer case may be in neutral when shifting between 4H-4LO.
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.
Condition 4WD warning lamp
System normal OFF
Lamp check Turns ON when ignition switch is turned ON.
Turns OFF after engine start.
4WD system malfunction ON
During self-diagnosis Flashes malfunction mode.
Large difference in diameter of front/
rear tires Flashes slow (1 flash / 2 seconds)
(Continues to flash until the ignition switch is turned OFF)
High fluid temperature in transfer case Flashes rapidly (2 flashes / 1 second)
(Continues to flash until fluid temperature returns to normal)
Revision: March 2010 2008 QX56

4WD SYSTEMDLN-15
< FUNCTION DIAGNOSIS > [ATX14B]
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TRANSFER FLUID TEMPERATURE SENSOR
The transfer fluid temperature sensor detects the trans fer fluid temperature and sends a signal to the transfer
control unit.
TRANSFER MOTOR
• The transfer motor drives the sub-oil pump to provi de 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 t he mainshaft. In other words, sufficient oil pressure
buildup does not occur when the vehicle is at standsti ll 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 vehi cle 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.
• 4WD shift switch, transmission range switch, Neutral-4LO switch, vehicle speed sensor and throttle position
sensor are used in conjunction with the transfer motor.
Transfer Motor Relay Operation
*: After 2.5 seconds have elapsed.
CLUTCH PRESSURE SOLENOID VALVE
The clutch pressure solenoid valve distributes front and rear torque in AUTO mode.
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.
TRANSFER CONTROL DEVICE
Integrates actuator motor and actuator position switch.
4WD shift switch A/T selector lever position Vehicle speed
(VSS) Accelerator pedal position Motor relay drive
command
2WD ———OFF
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 position 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
R position —— ON
R position —— ON
AUTO P or N position 0
0 - 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 posi-
tion 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
Revision: March 2010 2008 QX56

4WD SYSTEMDLN-17
< FUNCTION DIAGNOSIS > [ATX14B]
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CAN CommunicationINFOID:0000000001737099
Refer to LAN-51, "DTC Index".
1. A: Transfer shut off relay E69
B: Transfer shift low relay E47
C: Transfer shift high relay E46 2. A: Actuator
B: Transfer control device F58
C: Actuator lever
D: Transfer case 3. Wait detection switch F59
(View with transfer case removed)
4. A: Clutch pressure switch B: Line pressure switch
C: Transfer fluid temperature sensor
D: 2-4WD shift solenoid valve
E: Clutch pressure solenoid valve
(View with contro l valve removed
from transfer case) 5. A: Neutral 4LO switch F60
B: ATP switch F55
C: Transfer motor F57
D: Transfer terminal cord assembly F56
E: Oil filter 6. Combination meter M23, M24
A: 4WD warning lamp
B: ATP warning lamp
C: 4LO indicator lamp (located in in-
formation display)
D: 4WD shift indicator lamp
7. 4WD shift switch M141 8. Transfer control unit E142, E143 9. Transfer dropping resistor E135
Transfer motor relay E153, E154
(View with battery removed)
Revision: March 2010 2008 QX56

TRANSFER CONTROL UNITDLN-97
< ECU DIAGNOSIS > [ATX14B]
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CAUTION:
• If CAN COMM CIRCUIT [U1000] or CONTROL UNIT (CAN) [U1010] is displayed with other DTCs, first perform the trouble
diagnosis for CAN communication line.
• If ABS OP SIG [P1830], VDC OP SIG [P1831] or TCS OP SIG [P 1832] is displayed, first perform the trouble diagnosis for ABS
system.
• If VHCL SPEED SEN·AT [P1807] is displayed, firs t perform the trouble diagnosis for A/T system.
NOTE:
• If SHIFT ACT POSI SW [P1818] or SHIFT ACT CIR [P1819] is disp layed, 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 o n
transmission range switch. When there is no malfunction found in the electrical system, check the hydraulic system.
FLASH CODE CHART
[P1826] OIL TEMP SEN Signal voltage from transfer fluid temperature sen-
sor is abnormally high (Transfer fluid temperature is
abnormally low) while driving. Refer to
DLN-67.
[P1827] CLUTCH PRES SW • Improper signal from clutch pressure switch is in-
put due to open or short circuit.
• Malfunction occurs in clutch pressure switch or
hydraulic circuit. Refer to
DLN-70
.
[P1828] LINE PRES SW • Improper signal from line pressure switch is input
due to open or short circuit.
• Malfunction occurs in line pressure switch or hy-
draulic circuit. Refer to
DLN-73
.
[P1829] THROTTLE POSI SEN • Malfunction is detected in accelerator pedal posi-
tion signal that is output from ECM through CAN
communication.
• Signal voltage from accelerator pedal position sensor is abnormally high or low. Refer to
DLN-76
.
[P1830] ABS OP SIG Malfunction is detected in ABS operation signal that
is output from ABS actuator and electric unit (control
unit) through CAN communication. Refer to
DLN-77
.
[P1831] VDC OP SIG Malfunction is detected in VDC operation signal that
is output from ABS actuator and electric unit (control
unit) through CAN communication.
Refer to
DLN-78
.
[P1832] TCS OP SIG Malfunction is detected in TCS operation signal that
is output from ABS actuator and electric unit (control
unit) through CAN communication. Refer to
DLN-79
.
DTC CONSULT-III Diagnostic item is detected when... Reference
Flashing pattern
ItemDiagnostic item is detected when... Reference
2 Vehicle speed signal
(from A/T) • Malfunction is detected in output speed sensor signal that
is output from TCM through CAN communication.
• Improper signal is input while driving. Refer to DLN-26
.
3 Clutch pressure sole-
noid signal Proper voltage is not applied to clutch pressure solenoid
valve due to open or short circuit.
Refer to DLN-53
.
4 2-4WD solenoid signal Proper voltage is not applied to 2-4WD solenoid valve due
to open or short circuit. Refer to DLN-57
.
5 Transfer motor Transfer motor does not operate properly due to open or
short circuit in transfer motor or transfer motor relay.
Refer to DLN-61
.
6 Vehicle speed signal
(from ABS) • Malfunction is detected in vehicle speed signal that is out-
put from ABS actuator and electric unit (control unit)
through CAN communication.
• Improper signal is input while driving. Refer to DLN-27
.
7 CAN communication Malfunction has been detected from CAN communication
line. Refer to LAN-51
.
8 AD converter AD converter system of transfer control unit is malfunction-
ing. Refer to DLN-24
.
Revision: March 2010
2008 QX56

TRANSFER ASSEMBLYDLN-141
< DISASSEMBLY AND ASSEMBLY > [ATX14B]
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40. Retaining plate 41. Driven plate (10 sheet) 42. Drive plate (10 sheet)
43. Return spring assembly 44. Press flange 45. Thrust needle bearing
46. Snap ring 47. Retaining pin 48. L-H fork
49. 2-4 fork 50. Shift fork spring 51. Fork guide
52. Retainer pin 53. Shift rod
1. Dust cover 2. Rear oil seal 3. Rear case
4. Breather tube 5. Seal ring 6. Main oil pump cover
7. Inner gear 8. Outer gear 9. Main oil pump housing
10. D-ring 11. D-ring 12. Clutch piston
13. Thrust needle bearing race 14. Oil strainer 15. O-ring
16. Snap ring 17. Control valve assembly 18. Lip seal (large 5 pieces)
19. Lip seal (small 2 pieces) 20. Gasket 21. Filler plug
22. Oil filter stud 23. O-ring 24. Oil filter
25 ATP switch 26. Neutral-4LO switch 27. Oil pressure check plug
28. Harness bracket 29. Air breather hose clamp 30. Stem bleeder
31. Harness bracket 32. Center case 33. Mainshaft rear bearing
34. C-ring 35. Washer holder 36. Snap ring
37. Sub oil pump housing 38. Outer gear 39. Inner gear
WDIA0302E
Revision: March 2010 2008 QX56

DLN-152
< DISASSEMBLY AND ASSEMBLY >[ATX14B]
TRANSFER ASSEMBLY
22. Remove the mainshaft from the clutch drum and clutch hub
using suitable tool.
23. Remove the needle bearing and spacer from the mainshaft.
24. Remove the snap ring from the clutch hub using suitable tool.
25. Remove the oil pressure check plug from the oil pressure check port.
26. Apply air gradually from the oil pressure check port, and remove the clutch piston assembly from the center case.
27. Remove the thrust needle bearing race from the clutch piston by hooking a edge into 3 notches of the thrust needle bearing race
using suitable tool.
CAUTION:
Do not damage clutch piston or thrust needle bearing race.
SMT914C
WDIA0101E
WDIA0227E
SDIA2116E
SDIA2118E
Revision: March 2010 2008 QX56

TRANSFER ASSEMBLYDLN-159
< DISASSEMBLY AND ASSEMBLY > [ATX14B]
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1. Check the inner and outer circumference, tooth face, and side- face of the inner and outer gears for damage or abnormal wear.
2. Measure the side clearance between the main oil pump housing edge and the inner and outer gears.
3. Make sure the side clearance is within specification. If the mea- surement is out of specification, replace the inner and outer
gears with new ones as a set. Refer to DLN-140, "
Disassembly
and Assembly".
Sub-oil Pump
1. Check the inner and outer circumference, tooth face, and side-face of the inner and outer gears for damage or abnormal wear.
2. Measure the side clearance between the sub oil pump housing edge and the inner and outer gears.
3. Make sure the side clearance is within specification. If the mea- surement is out of specification, replace the inner and outer
gears with new ones as a set. Refer to DLN-140, "
Disassembly
and Assembly".
Control Valve
• Check resistance between the terminals of the clutch pressuresolenoid valve, 2-4WD shift solenoid valve, clutch pressure switch,
line pressure switch and the transfer fluid temperature sensor.
Refer to DLN-140, "
Disassembly and Assembly" (clutch pressure
solenoid valve), DLN-140, "
Disassembly and Assembly" (2-4WD
solenoid valve), DLN-140, "
Disassembly and Assembly" (clutch
pressure switch), DLN-140, "
Disassembly and Assembly" (line
pressure switch) and DLN-140, "
Disassembly and Assembly"
(transfer fluid temperature sensor).
• Check the sliding faces of the control valves and plugs for abnor- mality. If any is found, replace the control valve assembly with a
new one. Refer to DLN-140, "
Disassembly and Assembly".
CAUTION:
Replace control valve body together with clutch return spring
as a set. Specification : 0.015 - 0.035 mm (0.0006 - 0.0014 in)
SDIA2174E
Specification : 0.015 - 0.035 mm (0.0006 - 0.0014 in)SDIA2173E
WDIA0199E
SMT947C
Revision: March 2010
2008 QX56

TRANSFER ASSEMBLYDLN-163
< DISASSEMBLY AND ASSEMBLY > [ATX14B]
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f. With the lower body down, tighten the two bolts shown.
g. Apply ATF to the new O-rings, and install them to each solenoid valve, switch and terminal body.
CAUTION:
Do not reuse O-rings.
h. Install the following to the control valve assembly: • Clutch pressure solenoid valve
• Clutch pressure switch
• 2-4WD shift solenoid valve
• Line pressure switch
• Transfer fluid temperature sensor
10. Apply ATF to the new lip seals, and install them to the center case.
CAUTION:
• Do not reuse lip seals.
• There are 2 kinds of lip seals (lip seal of large inner diam-eter: 5 pieces, lip seal of small inner diameter: 2 pieces).
Confirm their position for installation.
11. Install the control valve assembly to the center case, and tighten to the specified torque. Refer to DLN-140, "
Disassembly and
Assembly".
CAUTION:
• Do not reuse any part that has been dropped or damaged.
• Make sure valve is assembled in the proper direction.
• Do not use a magnet becau se residual magnetism stays
during assembly.
12. Install the connector assembly into the center case, and secure with a snap ring.
13. Apply ATF to the new O-rings, and install them on the oil strainer.
CAUTION:
Do not reuse O-rings.
14. Install the oil strainer to the control valve assembly.
WDIA0198E
SDIA2123E
SDIA2121E
SDIA2122E
SDIA2782E
Revision: March 2010 2008 QX56