2010 INFINITI QX56 torque

TM-24
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
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 ControlINFOID:0000000005148514
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.
Shift Change System Diagram
PCIA0010E
PCIA0011E
PCIA0012E
Revision: April 20092010 QX56

A/T CONTROL SYSTEMTM-25
< FUNCTION DIAGNOSIS >
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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:0000000005148515
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 controlled by the torque conver ter 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.
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 position4 position 3 position 2 position
G ear p osit io n 54432
Lock-up ×– ×××
Slip lock-up ××–––
PCIA0014E
Revision: April 20092010 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 piston 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:0000000005148516
• 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:0000000005148517
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: April 20092010 QX56

A/T CONTROL SYSTEMTM-27
< FUNCTION DIAGNOSIS >
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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: April 20092010 QX56

DIAGNOSIS SYSTEM (TCM)TM-33
< FUNCTION DIAGNOSIS >
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4GR INCORRECT RA-
TIO • A/T cannot shift to 4GR.
P0734 P0734TM-62
5GR INCORRECT RA-
TIO• A/T cannot shift to 5GR.
P0735 P0735TM-64
TORQUE CONVERT-
ER• Normal voltage not applied to solenoid due to cut line,
short, or the like. P0740 P0740
TM-65
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-68
PC SOLENOID A• 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-69
TP SENSOR• TCM does not receive the proper accelerator pedal po-
sition signals (input by CAN communication) from
ECM. P1705 P1705
TM-71
FLUID TEMP SENSOR• During running, the ATF temperature sensor signal
voltage is excessively high or low. P1710 P0710
TM-73
VEHICLE SPEED SIG-
NAL• Signal (CAN communication) from vehicle speed sig-
nal not input due to cut line or the like.
• Unexpected signal input during running. P1721
—TM-76
INTERLOCK • Except during shift change, the gear position and ATF
pressure switch states are monitored and comparative
judgement made. P1730 P1730
TM-78
1GR E/BRAKING• Each ATF pressure switch and solenoid current is
monitored and if a pattern is detected having engine
braking 1GR other than in the "1" position, a malfunc-
tion is detected. P1731
—TM-80
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-82
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-84
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-86
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-88
L C BRAKE SOLENOID• Normal voltage not applied to solenoid due to function-
al malfunction, cut line, short, or the like. P1772 P1772
TM-90
Items (CONSULT-III
screen terms) Malfunction is detected when... TCM self-di-
agnosis OBD (DTC)
Reference
“TRANSMIS-
SION” with
CONSULT-III MIL indicator
lamp*1, “EN-
GINE” with
CONSULT-III or
GST
Revision: April 20092010 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-93
NO DTC IS DETECTED
FURTHER TESTING
MAY BE REQUIRED• No NG item has been detected.
XX —
Items (CONSULT-III
screen terms) Malfunction is detected when... TCM self-di-
agnosis OBD (DTC)
Reference
“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) XXX 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) XXXDegree 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
BRAKESW (ON-OFF display) X— X Stop lamp switch
GEAR —XXGear position recognized by the TCM updated
after gear-shifting.
ENGINE SPEED (rpm) XXX —
INPUT SPEED (rpm) XXX —
OUTPUT REV (rpm) XXX —
GEAR RATIO —XX —
TC SLIP SPEED (rpm) —XXDifference 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 1 (° C) —XX —
ATF TEMP 2 (° C) —XX —
BATTERY VOLT (V) X— X —
ATF PRES SW 1 (ON-OFF display) XXX —
ATF PRES SW 2 (ON-OFF display) XXX (for LC/B solenoid)
Revision: April 20092010 QX56

DIAGNOSIS SYSTEM (TCM)TM-39
< FUNCTION DIAGNOSIS >
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Erase Self-diagnosis
• In order to make it easier to find the cause of
hard-to-duplicate malfunctions, malfunction information is
stored into the control unit as necessary during use by the user. This memory is not erased no matter how
many times the ignition switch is turned ON and OFF.
• However, this information is erased by turning ignition switch OFF after executing self-diagnostics or by erasing the memory using the CONSULT-III.
No. Malfunctioning item No.Malfunctioning item
1 Output speed sensor TM-50
12 Interlock TM-78
2 Direct clutch solenoid TM-8613 1st engine braking TM-80
3 Torque converter TM-65, TM-6714 Starter relay TM-41
4 Line pressure solenoid TM-6915 Accelerator pedal position sensor TM-71
5 Input clutch solenoid TM-8216 Engine speed TM-53
6 Front brake solenoid TM-8417 CAN communication line TM-40
7 Low coast brake solenoid TM-90, TM-9218 1GR incorrect ratio TM-55
8 High and low reverse clutch solenoid TM-8819 2GR incorrect ratio TM-57
9 Transmission range switch TM-4520 3GR incorrect ratio TM-59
10 A/T fluid temperature sensor TM-7321 4GR incorrect ratio TM-61
11 Input speed sensor TM-4822 5GR incorrect ratio TM-63
Revision: April 20092010 QX56

P0740 TORQUE CONVERTERTM-65
< COMPONENT DIAGNOSIS >
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P0740 TORQUE CONVERTER
DescriptionINFOID:0000000005148593
• The torque converter clutch solenoid valve is activated, with the gear in D4, D5 by the TCM in response to
signals sent from the output speed sensor and accele rator pedal 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 Val ue in Data Monitor ModeINFOID:0000000005148594
On Board Diagnosis LogicINFOID:0000000005148595
• This is an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0740 TORQUE CONVERTER” wi th 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:0000000005148596
• Torque converter clutch solenoid valve
• Harness or connectors (The solenoid circuit is open or shorted.)
DTC Confirmation ProcedureINFOID:0000000005148597
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 procedure 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 vehic le uphill (increased engine load) will help maintain the driving
conditions required for this test.
4. If DTC is detected go to TM-65, "
Diagnosis Procedure".
WITH GST
Follow the procedure “With CONSULT-III”.
Diagnosis ProcedureINFOID:0000000005148598
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.
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: April 20092010 QX56