torque INFINITI QX56 2004 Factory Service Manual

AT-2Revision: August 20072004 QX56 CONSULT-II Reference Value ..............................109
On Board Diagnosis Logic ....................................109
Possible Cause .....................................................109
DTC Confirmation Procedure ...............................109
Diagnostic Procedure ...........................................110
DTC P0720 VEHICLE SPEED SENSOR A/T (REV-
OLUTION SENSOR) ...............................................112
Description ............................................................112
CONSULT-II Reference Value ..............................112
On Board Diagnosis Logic ....................................112
Possible Cause .....................................................112
DTC Confirmation Procedure ...............................112
Diagnostic Procedure ...........................................113
DTC P0725 ENGINE SPEED SIGNAL ...................115
Description ............................................................115
CONSULT-II Reference Value ..............................115
On Board Diagnosis Logic ....................................115
Possible Cause .....................................................115
DTC Confirmation Procedure ...............................115
Diagnostic Procedure ...........................................115
DTC P0740 TORQUE CONVERTER CLUTCH
SOLENOID VALVE .................................................118
Description ............................................................118
CONSULT-II Reference Value ..............................118
On Board Diagnosis Logic ....................................118
Possible Cause .....................................................118
DTC Confirmation Procedure ...............................118
Diagnostic Procedure ...........................................119
DTC P0744 A/T TCC S/V FUNCTION (LOCK-UP) .121
Description ............................................................121
CONSULT-II Reference Value ..............................121
On Board Diagnosis Logic ....................................121
Possible Cause .....................................................121
DTC Confirmation Procedure ...............................121
Diagnostic Procedure ...........................................122
DTC P0745 LINE PRESSURE SOLENOID VALVE .124
Description ............................................................124
CONSULT-II Reference Value ..............................124
On Board Diagnosis Logic ....................................124
Possible Cause .....................................................124
DTC Confirmation Procedure ...............................124
Diagnostic Procedure ...........................................125
DTC P1702 TRANSMISSION CONTROL MODULE
(RAM) ......................................................................127
Description ............................................................127
On Board Diagnosis Logic ....................................127
Possible Cause .....................................................127
DTC Confirmation Procedure ...............................127
Diagnostic Procedure ...........................................127
DTC P1703 TRANSMISSION CONTROL MODULE
(ROM) ......................................................................128
Description ............................................................128
On Board Diagnosis Logic ....................................128
Possible Cause .....................................................128
DTC Confirmation Procedure ...............................128
Diagnostic Procedure ...........................................128
DTC P1705 THROTTLE POSITION SENSOR .......129
Description ............................................................129
CONSULT-II Reference Value ..............................129On Board Diagnosis Logic .................................... 129
Possible Cause ..................................................... 129
DTC Confirmation Procedure ................................ 129
Diagnostic Procedure ............................................ 129
DTC P1710 A/T FLUID TEMPERATURE SENSOR
CIRCUIT .................................................................. 131
Description ............................................................ 131
CONSULT-II Reference Value ............................... 131
On Board Diagnosis Logic .................................... 131
Possible Cause ..................................................... 131
DTC Confirmation Procedure ................................ 131
Diagnostic Procedure ............................................ 132
Component Inspection .......................................... 133
DTC P1716 TURBINE REVOLUTION SENSOR .... 134
Description ............................................................ 134
CONSULT-II Reference Value ............................... 134
On Board Diagnosis Logic .................................... 134
Possible Cause ..................................................... 134
DTC Confirmation Procedure ................................ 134
Diagnostic Procedure ............................................ 135
DTC P1721 VEHICLE SPEED SENSOR MTR ....... 136
Description ............................................................ 136
CONSULT-II Reference Value ............................... 136
On Board Diagnosis Logic .................................... 136
Possible Cause ..................................................... 136
DTC Confirmation Procedure ................................ 136
Diagnostic Procedure ............................................ 137
DTC P1730 A/T INTERLOCK ................................. 139
Description ............................................................ 139
On Board Diagnosis Logic .................................... 139
Possible Cause ..................................................... 139
DTC Confirmation Procedure ................................ 139
Judgement of A/T Interlock ................................... 140
Diagnostic Procedure ............................................ 140
DTC P1731 A/T 1ST ENGINE BRAKING ............... 142
Description ............................................................ 142
CONSULT-II Reference Value ............................... 142
On Board Diagnosis Logic .................................... 142
Possible Cause ..................................................... 142
DTC Confirmation Procedure ................................ 142
Diagnostic Procedure ............................................ 143
DTC P1752 INPUT CLUTCH SOLENOID VALVE .. 145
Description ............................................................ 145
CONSULT-II Reference Value ............................... 145
On Board Diagnosis Logic .................................... 145
Possible Cause ..................................................... 145
DTC Confirmation Procedure ................................ 145
Diagnostic Procedure ............................................ 146
DTC P1754 INPUT CLUTCH SOLENOID VALVE
FUNCTION .............................................................. 148
Description ............................................................ 148
CONSULT-II Reference Value ............................... 148
On Board Diagnosis Logic .................................... 148
Possible Cause ..................................................... 148
DTC Confirmation Procedure ................................ 148
Diagnostic Procedure ............................................ 149
DTC P1757 FRONT BRAKE SOLENOID VALVE ... 151
Description ............................................................ 151
CONSULT-II Reference Value ............................... 151

AT-8
PRECAUTIONS
Revision: August 20072004 QX56
Precautions UCS002C3

Before connecting or disconnecting the A/T assembly har-
ness connector, turn ignition switch “OFF” and disconnect
negative battery cable. Because battery voltage is applied
to TCM even if ignition switch is turned “OFF”.

After performing each TROUBLE DIAGNOSIS, perform
“DTC (Diagnostic Trouble Code) CONFIRMATION PROCE-
DURE”.
If the repair is completed the DTC should not be displayed
in the “DTC CONFIRMATION PROCEDURE”.

Always use the specified brand of ATF. Refer to MA-10, "RECOMMENDED FLUIDS AND LUBRICANTS"
.

Use paper rags not cloth rags during work.

After replacing the ATF, dispose of the waste oil using the methods prescribed by law, ordinance, etc.

Before proceeding with disassembly, thoroughly clean the outside of the transaxle. It is important to pre-
vent the internal parts from becoming contaminated by dirt or other foreign matter.

Disassembly should be done in a clean work area.

Use lint-free cloth or towels for wiping parts clean. Common shop rags can leave fibers that could interfere
with the operation of the transaxle.

Place disassembled parts in order for easier and proper assembly.

All parts should be carefully cleaned with a general purpose, non-flammable solvent before inspection or
reassembly.

Gaskets, seals and O-rings should be replaced any time the transaxle is disassembled.

It is very important to perform functional tests whenever they are indicated.

The valve body contains precision parts and requires extreme care when parts are removed and serviced.
Place disassembled valve body parts in order for easier and proper assembly. Care will also prevent
springs and small parts from becoming scattered or lost.

Properly installed valves, sleeves, plugs, etc. will slide along bores in valve body under their own weight.

Before assembly, apply a coat of recommended ATF to all parts. Apply petroleum jelly to protect O-rings
and seals, or hold bearings and washers in place during assembly. Do not use grease.

Extreme care should be taken to avoid damage to O-rings, seals and gaskets when assembling.

After overhaul, refill the transaxle with new ATF.

When the A/T drain plug is removed, only some of the fluid is drained. Old A/T fluid will remain in torque
converter and ATF cooling system.
Always follow the procedures under “Changing A/T Fluid” in the AT section when changing A/T fluid. Refer
to AT-13, "
Changing A/T Fluid" , AT- 1 3 , "Checking A/T Fluid" .
SEF 2 89 H
SEF 2 17 U

AT-18
A/T CONTROL SYSTEM
Revision: August 20072004 QX56
A/T CONTROL SYSTEMPFP:31036
Cross-Sectional View (2WD models)UCS002CB
1. Front planetary gear 2. Mid planetary gear 3. Rear planetary gear
4. Direct clutch 5. High and low reverse clutch 6. Reverse brake
7. Drum support 8. Forward brake 9. Low coast brake
10. Input shaft 11. Torque converter 12. Oil pump
13. Front brake 14. 3rd one-way clutch 15. Input clutch
16. 1st one-way clutch 17. Control valve with TCM 18. Forward one-way clutch
19. Rear extension 20. Output shaft
SCIA5267E

A/T CONTROL SYSTEM
AT-19
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Revision: August 20072004 QX56
Cross-Sectional View (4WD models)UCS002C C
1. Front planetary gear 2. Mid planetary gear 3. Rear planetary gear
4. Direct clutch 5. High and low reverse clutch 6. Reverse brake
7. Drum support 8. Forward brake 9. Low coast brake
10. Input shaft 11. Torque converter 12. Oil pump
13. Front brake 14. 3rd one-way clutch 15. Input clutch
16. 1st one-way clutch 17. Control valve with TCM 18. Forward one-way clutch
19. Adapter case 20. Output shaft
SCIA5268E

AT-22
A/T CONTROL SYSTEM
Revision: August 20072004 QX56
POWER TRANSMISSION
“N” Position
Since both the forward brake and the reverse brake are released, torque from the input shaft drive is not trans-
mitted to the output shaft.
“P” Position

The same as for the “N” position, both the forward brake and the reverse brake are released, so torque
from the input shaft drive is not transmitted to the output shaft.

The parking pawl linked with the select lever meshes with the parking gear and fastens the output shaft
mechanically.
LCIA0316E
1. Front brake 2. Input clutch 3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch 9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear 12. Input shaft
13. Mid internal gear 14. Front internal gear 15. Rear carrier
16. Rear sun gear 17. Mid sun gear 18. Front carrier
19. Mid carrier 20. Rear internal gear 21. Output shaft
22. Parking gear 23. Parking pawl
PCIA0003J

A/T CONTROL SYSTEM
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Revision: August 20072004 QX56
TCM FunctionUCS002CE
The function of the TCM is to:

Receive input signals sent from various switches and sensors.

Determine required line pressure, shifting point, lock-up operation, and engine brake operation.

Send required output signals to the respective solenoids.
CONTROL SYSTEM OUTLINE
The automatic transmission senses vehicle operating conditions through various sensors or signals. It always
controls the optimum shift position and reduces shifting and lock-up shocks.
CONTROL SYSTEM DIAGRAM
SENSORS (or SIGNALS)


TCM


ACTUATORS
PNP switch
Accelerator pedal position sensor
Closed throttle position signal
Wide open throttle position signal
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed signal
Stop lamp switch signal
Turbine revolution sensor
1st position switch signal
4th position switch signalShift control
Line pressure control
Lock-up control
Engine brake control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication line
Duet-EA control
CAN systemInput clutch solenoid valve
Direct clutch solenoid valve
Front brake solenoid valve
High and low reverse clutch
solenoid valve
Low coast brake solenoid valve
Torque converter clutch solenoid
valve
Line pressure solenoid valve
A/T CHECK indicator lamp
Sta rte r re lay
Back-up lamp relay
LCIA0317E

A/T CONTROL SYSTEM
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Line Pressure ControlUCS002C H

When an input torque signal equivalent to the engine drive force is sent from the ECM to the TCM, the
TCM controls the line pressure solenoid.

This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the
pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the
driving state.
LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC
PATTERN

The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the
driving state.

In order to obtain the most appropriate line pressure characteristic to meet the current driving state, the
TCM controls the line pressure solenoid current valve and thus controls the line pressure.
Normal Control
Each clutch is adjusted to the necessary pressure to match the
engine drive force.
Back-up Control (Engine Brake)
When the select operation is performed during driving and the trans-
mission is shifted down, the line pressure is set according to the
vehicle speed.
PCIA0007E
PCIA0008E
PCIA0009E

AT-34
A/T CONTROL SYSTEM
Revision: August 20072004 QX56
During Shift Change
The necessary and adequate line pressure for shift change is set.
For this reason, line pressure pattern setting corresponds to input
torque and gearshift selection. Also, line pressure characteristic is
set according to engine speed, during engine brake operation.
At Low Fluid Temperature
When the A/T fluid temperature drops below the prescribed tempera-
ture, in order to speed up the action of each friction element, the line
pressure is set higher than the normal line pressure characteristic.
Shift ControlUCS002CI
The clutch pressure control solenoid is controlled by the signals from the switches and sensors. Thus, the
clutch pressure is adjusted to be appropriate to the engine load state and vehicle driving state. It becomes
possible to finely control the clutch hydraulic pressure with high precision and a smoother shift change charac-
teristic is attained.
SHIFT CHANGE
The clutch is controlled with the optimum timing and oil pressure by the engine speed, engine torque informa-
tion, etc.
PCIA0010E
PCIA0 011 E
PCIA0012E

A/T CONTROL SYSTEM
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Shift Change System Diagram
*1: Full phase real-time feedback control monitors movement of gear ratio at gear change, and controls oil
pressure at real-time to achieve the best gear ratio.
Lock-up ControlUCS002CJ
The torque converter clutch piston in the torque converter is engaged to eliminate torque converter slip to
increase power transmission efficiency.
The torque converter clutch control valve operation is controlled by the torque converter clutch solenoid valve,
which is controlled by a signal from TCM, and the torque converter clutch control valve engages or releases
the torque converter clutch piston.
Lock-up Operation Condition Table
TORQUE CONVERTER CLUTCH CONTROL VALVE CONTROL
Lock-up Control System Diagram
Lock-up Released

In the lock-up released state, the torque converter clutch control valve is set into the unlocked state by the
torque converter clutch solenoid and the lock-up apply pressure is drained.
In this way, the torque converter clutch piston is not coupled.
PCIA0013E
Select lever D position 4 position 3 position 2 position
Gear position 5 4 4 3 2
Lock-up×–×××
Slip lock-up××–––
PCIA0014E

AT-36
A/T CONTROL SYSTEM
Revision: August 20072004 QX56
Lock-up Applied

In the lock-up applied state, the torque converter clutch control valve is set into the locked state by the
torque converter clutch solenoid and lock-up apply pressure is generated.
In this way, the torque converter clutch piston is pressed and coupled.
SMOOTH LOCK-UP CONTROL
When shifting from the lock-up released state to the lock-up applied state, the current output to the torque con-
verter clutch solenoid is controlled with the TCM. In this way, when shifting to the lock-up applied state, the
torque converter clutch is temporarily set to the half-clutched state to reduce the shock.
Half-clutched State

The current output from the TCM to the torque converter clutch solenoid is varied to gradually increase
the torque converter clutch solenoid pressure.
In this way, the lock-up apply pressure gradually rises and while the torque converter clutch piston is put
into half-clutched status, the torque converter clutch piston operating pressure is increased and the cou-
pling is completed smoothly.
Slip Lock-up Control

In the slip region, the torque converter clutch solenoid current is controlled with the TCM to put it into the
half-clutched state. This absorbs the engine torque fluctuation and lock-up operates from low speed.
This raises the fuel efficiency for 4th and 5th gears at both low speed and when the accelerator has a low
degree of opening.