torque INFINITI QX56 2009 Factory Service Manual

A/T CONTROL SYSTEMTM-25
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*1: Full phase real-time feedback control monitors move ment of gear ratio at gear change, and controls oil
pressure at real-time to achieve the best gear ratio.
Lock-up ControlINFOID:0000000003771813
The torque converter clutch piston in the torque conv erter is engaged to eliminate torque converter slip to
increase power transmission efficiency.
The torque converter clutch control valve operation is c ontrolled by the torque converter clutch solenoid valve,
which is controlled by a signal from TCM, and the to rque 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.
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
PCIA0013E
Select lever D position 4 position 3 position 2 position
Gear position 54432
Lock-up ×– ×××
Slip lock-up ××–––
PCIA0014E
Revision: December 20092009 QX56

TM-26
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
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 th is 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 converte r 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 pi ston operating pressure is increased and the coupling 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 tor que fluctuation and lock-up operates from low speed.
This raises the fuel efficiency for 4GR and 5GR at both low speed and when the accelerator has a low
degree of opening.
Engine Brake ControlINFOID:0000000003771814
 The forward one-way clutch transmits the drive force from the engine to the rear wheels. But the reverse
drive from the rear wheels is not transmitted to the engine because the one-way clutch is idling.
Therefore, the low coast brake solenoid is operated to prevent the forward one-way clutch from idling and
the engine brake is operated in the same manner as conventionally.
 The operation of the low coast brake solenoid switches the low coast brake switching valve and controls the
coupling and releasing of the low coast brake.
The low coast brake reducing valve contro ls the low coast brake coupling force.
Control ValveINFOID:0000000003771815
FUNCTION OF CONTROL VALVE
SCIA1520E
Name Function
Torque converter regulator valve In order to prevent the pressure supplied to the torque converter from being excessive,
the line pressure is adjusted to the optimum pressure (torque converter operating pres-
sure).
Pressure regu lator valve
Pressure regulator plug
Pressure regu lator sleeve Adjusts the oil discharged from the oil pump to the optimum pressure (line pressure) for
the driving state.
Front brake control valve When the front brake is coupled, adjusts the line pressure to the optimum pressure (front
brake pressure) and supplies it to the front brake. (In 1GR, 2GR, 3GR, and 5GR, adjusts
the clutch pressure.)
Accumulator control valve Adjusts the pressure (accumulator control pressure) acting on the accumulator piston
and low coast reducing valve to the pressure appropriate to the driving state.
Revision: December 20092009 QX56

A/T CONTROL SYSTEMTM-27
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FUNCTION OF PRESSURE SWITCH
Pilot valve A Adjusts the line pressure and produces the constant pressure (pilot pressure) required
for line pressure control, shift change control, and lock-up control.
Pilot valve B Adjusts the line pressure and produces the constant pressure (pilot pressure) required
for shift change control.
Low coast brake switching valve During engine braking, supplies the line pressure to the low coast brake reducing valve.
Low coast brake reducing valve When the low coast brake is coupled, adjusts the line pressure to the optimum pressure
(low coast brake pressure) and supplies it to the low coast brake.
N-R accumulator Produces the stabilizing pressure for when N-R is selected.
Direct clutch piston switching valve Operates in 4GR and switches the direct clutch coupling capacity.
High and low reverse clutch control valve When the high and low reverse clutch is coupled, adjusts the line pressure to the opti-
mum pressure (high and low reverse clutch pressure) and supplies it to the high and low
reverse clutch. (In 1GR, 3GR, 4GR and 5GR, adjusts the clutch pressure.)
Input clutch control valve When the input clutch is coupled, adjusts the line pressure to the optimum pressure (in-
put clutch pressure) and supplies it to the input clutch. (In 4GR and 5GR, adjusts the
clutch pressure.)
Direct clutch control valve When the direct clutch is coupled, adjusts the line pressure to the optimum pressure (di-
rect clutch pressure) and supplies it to the direct clutch. (In 2GR, 3GR, and 4GR, adjusts
the clutch pressure.)
TCC control valve
TCC control plug
TCC control sleeve Switches the lock-up to operating or released. Also, by performing the lock-up operation
transiently, lock-up smoothly.
Torque converter lubrication valve Operates during lock-up to switch the torque converter, cooling, and lubrication system
oil path.
Cool bypass valve Allows excess oil to bypass cooler circuit without being fed into it.
Line pressure relief valve Discharges excess oil from line pressure circuit.
N-D accumulator Produces the stabilizing pressure for when N-D is selected.
Manual valve Sends line pressure to each circuit according to the select position. The circuits to which
the line pressure is not sent drain.
Name Function
Name Function
Pressure switch 2 (LC/B) Detects any malfunction in the low coast brake hydraulic pressure. When it detects any
malfunction, it puts the system into fail-safe mode.
Revision: December 20092009 QX56

DIAGNOSIS SYSTEM (TCM)TM-33
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4GR INCORRECT RA-
TIO  A/T cannot shift to 4th gear P0734 P0734
TM-61
5GR INCORRECT RA-
TIO A/T cannot shift to 5th gear P0735 P0735
TM-63
TORQUE CONVERT-
ER Normal voltage not applied to solenoid due to cut line,
short, or the like P0740 P0740
TM-64
TORQUE CONVERT-
ER A/T cannot perform lock-up even if electrical circuit is
good.
 TCM detects as irregular by comparing difference val-
ue with slip rotation. P0744 P0744*2
TM-67
PC SOLENOID Normal voltage not applied to solenoid due to cut line,
short, or the like
 TCM detects as irregular by comparing target value
with monitor value. P0745 P0745
TM-68
TP SENSOR TCM does not receive the proper accelerator pedal po-
sition signals (input by CAN communication) from
ECM. P1705 P1705
TM-70
TRANS FLUID TEMP
SEN During running, the ATF temperature sensor signal
voltage is excessively high or low P1710 P0710
TM-72
VEHICLE SPEED SIG-
NAL Signal (CAN communication) from vehicle speed sen-
sor MTR not input due to cut line or the like
 Unexpected signal input during running P1721 —
TM-74
INTERLOCK Except during shift change, the gear position and ATF
pressure switch states are monitored and comparative
judgement made. P1730 P1730
TM-76
1GR E/BRAKING Each ATF pressure switch and solenoid current is
monitored and if a pattern is detected having engine
braking 1st gear other than in the "1" position, a mal-
function is detected. P1731 —
TM-78
INPUT CLUTCH SOLE-
NOID Normal voltage not applied to solenoid due to function-
al malfunction, cut line, short, or the like
 TCM detects as irregular by comparing target value
with monitor value. P1752 P1752
TM-80
FR BRAKE SOLENOID Normal voltage not applied to solenoid due to function-
al malfunction, cut line, short, or the like
 TCM detects as irregular by comparing target value
with monitor value. P1757 P1757
TM-82
DRCT CLUTCH SOLE-
NOID Normal voltage not applied to solenoid due to cut line,
short, or the like
 TCM detects as irregular by comparing target value
with monitor value. P1762 P1762
TM-84
HLR CLUTCH SOLE-
NOID Normal voltage not applied to solenoid due to function-
al malfunction, cut line, short, or the like
 TCM detects as irregular by comparing target value
with monitor value. P1767 P1767
TM-86
L C BRAKE SOLENOID Normal voltage not applied to solenoid due to function-
al malfunction, cut line, short, or the like P1772 P1772
TM-88
Items (CONSULT-III
screen terms) Malfunction is detected when... TCM self-di-
agnosis OBD (DTC)
Reference page
“TRANSMIS-
SION” with
CONSULT-III MIL indicator
lamp*1, “EN-
GINE” with
CONSULT-III or
GST
Revision: December 20092009 QX56

TM-34
< FUNCTION DIAGNOSIS >
DIAGNOSIS SYSTEM (TCM)
*1: Refer to EC-55, "Malfunction Indicator Lamp (MIL)".
*2:These malfunctions cannot be displayed MIL if another malfunction is assigned to MIL.
DATA MONITOR MODE
Display Items List
X: Standard, —: Not applicable
L C BRAKE SOLENOID  TCM detects an improper voltage drop when it tries to
operate the solenoid valve.
 Condition of ATF pressure switch 2 is different from
monitor value, and relation between gear position and
actual gear ratio is irregular. P1774 P1774*2
TM-90
NO DTC IS DETECTED
FURTHER TESTING
MAY BE REQUIRED No NG item has been detected. X X
Items (CONSULT-III
screen terms) Malfunction is detected when... TCM self-di-
agnosis OBD (DTC)
Reference page
“TRANSMIS-
SION” with
CONSULT-III MIL indicator
lamp*1, “EN-
GINE” with
CONSULT-III or
GST
Monitored item (Unit) Monitor Item Selection
Remarks
ECU IN-
PUT SIG-
NALS MAIN SIG-
NALS SELEC-
TION
FROM
MENU
VHCL/S SE·A/T (km/h) X X X Output speed sensor
VHCL/S SE·MTR (km/h) X — X
ACCELE POSI (0.0/8) X — X Accelerator pedal position signal
THROTTLE POSI (0.0/8) X X X Degree of opening for accelerator recognized by
the TCM
For fail-safe operation, the specific value used
for control is displayed.
CLSD THL POS (ON-OFF display) X — X Signal input with CAN communications
W/O THL POS (ON-OFF display) X — X
BRAKE SW (ON-OFF display) X — X Stop lamp switch
GEAR — X X Gear position recognized by the TCM updated
after gear-shifting
ENGINE SPEED (rpm) X X X
INPUT SPEED (rpm) X X X
OUTPUT REV (rpm) X X X
GEAR RATIO — X X
TC SLIP SPEED (rpm) — X X Difference between engine speed and torque
converter input shaft speed
F SUN GR REV (rpm) — — X
F CARR GR REV (rpm) — — X
ATF TEMP SE 1 (V) X — X
ATF TEMP SE 2 (V) X — X
ATF TEMP 1 ( °C) — X X
ATF TEMP 2 ( °C) — X X
BATTERY VOLT (V) X — X
ATF PRES SW 2 (ON-OFF display) X X X (for LC/B solenoid)
Revision: December 20092009 QX56

TM-64
< COMPONENT DIAGNOSIS >
P0740 TORQUE CONVERTER
P0740 TORQUE CONVERTER
DescriptionINFOID:0000000003771890
 The torque converter clutch solenoid valve is activated, with the gear in D4, D5 by the TCM in response to
signals sent from the vehicle speed sensor and accelera tor pedal position sensor (throttle position sensor).
Torque converter clutch piston operation will then be controlled.
 Lock-up operation, however, is prohibited when A/T fluid temperature is too low.
 When the accelerator pedal is depressed (less than 1/8) in lock-up condition, the engine speed should not
change abruptly. If there is a big jump in engine speed, there is no lock-up.
CONSULT-III Reference Value in Data Monitor ModeINFOID:0000000003771891
On Board Diagnosis LogicINFOID:0000000003771892
 This is an OBD-II self-diagnostic item.
 Diagnostic trouble code “P0740” with CONSULT-III is detected under the following conditions.
- When TCM detects an improper voltage drop when it tries to operate the solenoid valve.
- When TCM detects as irregular by comparing target value with monitor value.
Possible CauseINFOID:0000000003771893
 Torque converter clutch solenoid valve
 Harness or connectors (The solenoid circuit is open or shorted.)
DTC Confirmation ProcedureINFOID:0000000003771894
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If “DTC Confirmation Procedure” has been previously performed, always turn ignition switch “OFF”
and wait at least 10 seconds before performing the next test.
After the repair, perform the following proc edure to confirm the malfunction is eliminated.
WITH CONSULT-III
1. Turn ignition switch “ON”. (Do not start engine.)
2. Select “DATA MONITOR” mode for “ENGINE” with CONSULT-III.
3. Start engine and maintain the following conditions for at least 5 consecutive seconds.
VHCL/S SE-A/T: 80 km/h (50 MPH) or more
ACCELE POSI: 0.5/8 - 1.0/8
SLCT LVR POSI: “D” position
Driving location: Driving the vehicle uphill (increased engine load) will help maintain the driving
conditions required for this test.
4. If DTC is detected go to TM-64, "Diagnosis Procedure"
.
WITH GST
Follow the procedure “With CONSULT-III”.
Diagnosis ProcedureINFOID:0000000003771895
1.CHECK INPUT SIGNAL
With CONSULT-III
1. Turn ignition switch “ON”.
2. Select “MAIN SIGNALS” in “DATA MONITO R” mode for “TRANSMISSION” with CONSULT-III.
3. Start engine.
Item name Condition Display value (Approx.)
TCC SOLENOID When performing slip lock-up 0.2 - 0.4 A
When performing lock-up 0.4 - 0.6 A
Revision: December 20092009 QX56

P0740 TORQUE CONVERTERTM-65
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4. Read out the value of “TCC SOLENOID” while driving.
OK or NG
OK >> GO TO 4.
NG >> GO TO 2.
2.CHECK TCM POWER SUPPLY AND GROUND CIRCUIT
Check TCM power supply and ground circuit. Refer to TM-92, "Diagnosis Procedure"
.
OK or NG
OK >> GO TO 3.
NG >> Repair or replace damaged parts.
3.DETECT MALFUNCTIONING ITEM
Check the following items:
 The A/T assembly harness connector pin terminals for damage or loose connection with harness connector.
OK or NG
OK >> Replace the control valve with TCM. Refer to TM-203, "Control Valve with TCM and A/T Fluid
Temperature Sensor 2".
NG >> Repair or replace damaged parts.
4.CHECK DTC
Perform “DTC Confirmation Procedure”.
 Refer to TM-64, "DTC Confirmation Procedure"
.
OK or NG
OK >> INSPECTION END
NG >> GO TO 2.
Item name Condition Display value (Approx.)
TCC SOLENOID When performing slip lock-up 0.2 - 0.4 A
When performing lock-up 0.4 - 0.6 A
Revision: December 20092009 QX56

TM-66
< COMPONENT DIAGNOSIS >
P0744 TORQUE CONVERTER
P0744 TORQUE CONVERTER
DescriptionINFOID:0000000003771896
This malfunction is detected when the A/T does not lock-up. This is not only caused by electrical malfunction
(circuits open or shorted) but also by mechanical malfunc tion such as control valve sticking, improper solenoid
valve operation, etc.
CONSULT-III Reference Value in Data Monitor ModeINFOID:0000000003771897
On Board Diagn osis LogicINFOID:0000000003771898
 This is an OBD-II self-diagnostic item.
 Diagnostic trouble code “P0744” with CONSULT-III is detected under the following conditions.
- When A/T cannot perform lock-up even if electrical circuit is good.
- When TCM detects as irregular by comparing difference value with slip rotation.
Possible CauseINFOID:0000000003771899
 Harness or connectors
(The solenoid circuit is open or shorted.)
 Torque converter clutch solenoid valve
 Hydraulic control circuit
DTC Confirmation ProcedureINFOID:0000000003771900
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If “DTC Confirmation Procedure” has been previously performed, always turn ignition switch “OFF”
and wait at least 10 seconds before performing the next test.
After the repair, perform the following proc edure to confirm the malfunction is eliminated.
WITH CONSULT-III
1. Start engine and Select “TCC S/V FNCTN CHECK” of “DTC WORK SUPPORT” mode for “TRANSMIS-
SION” with CONSULT-III and touch “START”.
2. Accelerate vehicle to more than 80 km/h (50 MPH) and maintain the following condition continuously until “TESTING” has turned to “COMPLETE”. (It will take approximately 30 seconds after “TESTING” shows.)
ACCELE POSI: More than 1.0/8 (at all times during step 4)
TCC SOLENOID: 0.4 - 0.6 A
SLCT LVR POSI: “D” position
[Reference speed: Constant speed of more than 80 km/h (50 MPH)]
- Make sure “GEAR” shows “5”.
- For shift schedule, refer to TM-291, "Vehicle Speed at Which Lock-up Occurs/Releases"
.
- If “TESTING” does not ap pear on CONSULT-III for a long ti me, select “SELF-DIAG RESULTS”. In
case a 1st trip DTC other than P0744 is shown, refer to applicable “TROUBLE DIAGNOSIS FOR
DTC”.
3. Make sure that “OK” is displayed. (If “NG” is displayed, refer to “DIAGNOSTIC PROCEDURE”.)
Refer to TM-67, "Diagnosis Procedure"
.
Refer to shift schedule, TM-291, "Vehicle Speed at Which Lock-up Occurs/Releases"
.
WITH GST
Follow the procedure “With CONSULT-III”.
Item name Condition Display value (Approx.)
TCC SOLENOID When performing slip lock-up 0.2 - 0.4 A
When performing lock-up 0.4 - 0.6 A
Revision: December 20092009 QX56

P0744 TORQUE CONVERTERTM-67
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Diagnosis ProcedureINFOID:0000000003771901
1.CHECK INPUT SIGNAL
With CONSULT-III
1. Turn ignition switch “ON”.
2. Select “MAIN SIGNALS” in “DATA MONITOR” mode for “TRANSMISSION” with CONSULT-III.
3. Start the engine.
4. Read out the value of “TCC SOLENOID” while driving.
OK or NG
OK >> GO TO 4.
NG >> GO TO 2.
2.CHECK TCM POWER SUPPLY AND GROUND CIRCUIT
Check TCM power supply and ground circuit. Refer to TM-92, "Diagnosis Procedure"
.
OK or NG
OK >> GO TO 3.
NG >> Repair or replace damaged parts.
3.DETECT MALFUNCTIONING ITEM
Check the following items:
 The A/T assembly harness connector pin terminals for damage or loose connection with harness connector.
OK or NG
OK >> Replace the control valve with TCM. Refer to TM-203, "Control Valve with TCM and A/T Fluid
Temperature Sensor 2".
NG >> Repair or replace damaged parts.
4.CHECK DTC
Perform “DTC Confirmation Procedure”.
 Refer to TM-66, "DTC Confirmation Procedure"
.
OK or NG
OK >> INSPECTION END
NG >> GO TO 2.
Item name Condition Display value (Approx.)
TCC SOLENOID When performing slip lock-up 0.2 - 0.4 A
When performing lock-up 0.4 - 0.6 A
Revision: December 20092009 QX56

TM-116
< ECU DIAGNOSIS >
TCM
Even when the electronic circuits are normal, under special conditions (for example, when slamming on the
brake with the wheels spinning drastically and stopping t he tire rotation), the transmission can go into fail-safe
mode. If this happens, switch “OFF” the ignition switch for 10 seconds, then switch it “ON” again to return to
the normal shift pattern. Therefore, the customer's v ehicle has returned to normal, so handle according to the
“diagnostics flow” (Refer to TM-5, "Work Flow"
).
FAIL-SAFE FUNCTION
If any malfunction occurs in a sensor or solenoid, th is function controls the A/T to mark driving possible.
Output Speed Sensor
 Signals are input from two systems - from output s peed sensor installed on the transmission and from com-
bination meter so normal driving is possible even if ther e is a malfunction in one of the systems. And if output
speed sensor has unusual cases, 5GR is prohibited.
Accelerator Peda l Position Sensor
 If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM according
to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow sys-
tems, the engine speed is fixed by ECM to a pre-determined engine speed to make driving possible.
Throttle Position Sensor
 If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM according
to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow sys-
tems, the accelerator opening angle is controlled by the idle signal sent from the ECM which is based on
input indicating either idle condition or off-idle condition (pre-determined accelerator opening) in order to
make driving possible.
Transmission Range Switch
 In the unlikely event that a malfunction signal enters t he TCM, the position indicator is switched “OFF”, the
starter relay is switched “OFF” (starter starting is disabled), the back-up lamp relay switched “OFF” (back-up
lamp is OFF) and the position is fixed to the “D” range to make driving possible.
Starter Relay
 The starter relay is switched “OFF”. (Starter starting is disabled.)
Interlock
 If there is an interlock judgment malfunction, the trans mission is fixed in 2GR to make driving possible.
NOTE:
When the vehicle is driven fixed in 2GR, a input speed sensor malfunction is displayed, but this is
not a input speed sensor malfunction.
 When the interlock is detected at the 3GR or more, it is locked at the 2GR.
1st Engine Braking
 When there is an 1st gear engine brake judgment malfunc tion, the low coast brake solenoid is switched
“OFF” to avoid the engine brake operation.
Line Pressure Solenoid
 The solenoid is switched “OFF” and the line pressure is se t to the maximum hydraulic pressure to make driv-
ing possible.
Torque Converter Clutch Solenoid
 The solenoid is switched “OFF” to release the lock-up.
Low Coast Brake Solenoid
 When a (electrical or functional) malfunction occurs, in order to make driving possible, the engine brake is not applied in 1GR and 2GR.
Input Clutch Solenoid
 If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4GR to make driving possible.
Direct Clutch Solenoid
 If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4GR to make driving possible.
Front Brake Solenoid
 If a (electrical or functional) malfunction occurs with the solenoid “ON”, in order to make driving possible, the
A/T is held in 5GR; if the solenoid is OFF, 4GR.
Revision: December 20092009 QX56