2009 INFINITI QX56 torque

TM-12
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
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 br ake 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.
“D”, “4”, “3”, “2” Positions 1GR
 The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
 The 1st one-way clutch regulates reverse rotation of the rear sun gear.
 The 3rd one-way clutch regulates reverse rotation of the front sun gear.
 During deceleration, the mid sun gear turns forward, so the forward one-way clutch idles and the engine
brake is not activated.
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
Revision: December 20092009 QX56

A/T CONTROL SYSTEMTM-21
< FUNCTION DIAGNOSIS >
CEF
G H
I
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K L
M A
B
TM
N
O P
CONTROL SYSTEM DIAGRAM
CAN CommunicationINFOID:0000000003771809
SYSTEM DESCRIPTION
CAN (Controller Area Network) is a serial communication li ne for real time application. It is an on-vehicle mul-
tiplex communication line with high data communication speed and excellent error detection ability. Many elec-
tronic control units are equipped onto a vehicle, and each control unit shares information and links with other
control units during operation (not independent). In CAN communication, control units are connected with 2
communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only. For details, refer to LAN-4,
"System Description".
SENSORS (or SIGNALS)
⇒TCM
⇒ACTUATORS
Transmission range switch
Accelerator pedal position sensor
Closed throttle position signal
Wide open throttle position signal
Engine speed signal
A/T fluid temperature sensor
Output speed sensor
Vehicle speed signal
Stop lamp switch signal
Input speed sensor
1st position switch signal
4th position switch signal
ATF pressure switch 2 signal
Tow mode switch signal Shift control
Line pressure control
Lock-up control
Engine brake control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-III co
mmunication
line
Duet-EA control
CAN system Input clutch solenoid valve
Direct clutch solenoid valve
Front brake solenoid valve
High and low reverse clutch sole-
noid valve
Low coast brake solenoid valve
Torque converter clutch solenoid
valve
Line pressure solenoid valve
A/T CHECK indicator lamp
Starter relay
Back-up lamp relay
JSDIA1315GB
Revision: December 20092009 QX56

TM-22
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
Input/Output Signal of TCM
INFOID:0000000003771810
*1: Spare for output speed sensor.
*2: Spare for accelerator pedal position signal
*3: If these input and output signals are different, the TCM triggers the fail-safe function.
*4: CAN comm unications
*5: Used as a condition for starting self-diagnostics; if self-diagnostics are not started, it is judged that there is some kin d of error.
*6: A/T fluid temperature sensor 2 does not have any function.
Line Pressure ControlINFOID:0000000003771811
 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.
Control item Line
pres- sure
control Vehicle
speed
control S h i f t
control Lock-up
control Engine
brake
control Fail-safe
function (*3) Self-diag-
nostics
function
Input Accelerator pedal position signal
(*4)XXXXX X X
Output speed sensor X X X X X X
Vehicle speed signal
(*1) (*4)XXXX X
Closed throttle position signal
(*4)(*2) X (*2) X X (*2) X (*5) X
Wide open throttle position signal
(*4)(*2) X (*2) X (*2) X (*5) X
Input speed sensor 1 X X X X X
Input speed sensor 2
(for 4th speed only) XX X X X
Engine speed signals
(*4)XX
Transmission range switch X X X X X X X
Stop lamp switch signal
(*4)XXX (*5) X
A/T fluid temperature sensors 1, 2 (*6) X X X X X X X
ASCD Operation signal
(*4)XXXX
Overdrive cancel sig-
nal
(*4)XXX
TCM power supply voltage signal X X X X X X
Output Direct clutch solenoid X X X X
Input clutch solenoid X X X X
High and low reverse clutch solenoid X X X X
Front brake solenoid X X X X
Low coast brake solenoid (ATF pressure
switch 2)
XX X X X
Line pressure solenoid X X X X X X X
TCC solenoid X X X
Starter relay XX
Revision: December 20092009 QX56

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:0000000003771812
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 pressu re 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: December 20092009 QX56

A/T CONTROL SYSTEMTM-25
< FUNCTION DIAGNOSIS >
CEF
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K L
M A
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TM
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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
< FUNCTION DIAGNOSIS >
CEF
G H
I
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K L
M A
B
TM
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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
< FUNCTION DIAGNOSIS >
CEF
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M A
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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