2007 INFINITI QX56 clutch

A/T CONTROL SYSTEM
AT-37
< SERVICE INFORMATION >
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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 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 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.
Engine Brake ControlINFOID:0000000003532236
• 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 controls the low coast brake coupling force.
Control ValveINFOID:0000000003532237
FUNCTION OF CONTROL VALVE
SCIA1520E
Name Function
Torque converter regulator valveIn 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 regulator valve
Pressure regulator plug
Pressure regulator sleeveAdjusts the oil discharged from the oil pump to the optimum pressure (line pressure) for
the driving state.
Front brake control valveWhen the front brake is coupled, adjusts the line pressure to the optimum pressure (front
brake pressure) and supplies it to the front brake. (In 1st, 2nd, 3rd, and 5th gears, adjusts
the clutch pressure.)
Accumulator control valveAdjusts the pressure (accumulator control pressure) acting on the accumulator piston
and low coast reducing valve to the pressure appropriate to the driving state.

AT-38
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
FUNCTION OF PRESSURE SWITCH
Pilot valve AAdjusts the line pressure and produces the constant pressure (pilot pressure) required
for line pressure control, shift change control, and lock-up control.
Pilot valve BAdjusts 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 valveWhen 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 4th gear and switches the direct clutch coupling capacity.
High and low reverse clutch control valveWhen 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 1st, 3rd, 4th and 5th gears, adjusts the clutch pressure.)
Input clutch control valveWhen 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 4th and 5th gears, adjusts the
clutch pressure.)
Direct clutch control valveWhen 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 2nd, 3rd, and 4th gears, ad-
justs the clutch pressure.)
TCC control valve
TCC control plug
TCC control sleeveSwitches the lock-up to operating or released. Also, by performing the lock-up operation
transiently, lock-up smoothly.
Torque converter lubrication valveOperates 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 valveSends 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 1 (FR/B)Detects any malfunction in the front brake hydraulic pressure. When it detects any mal-
function, it puts the system into fail-safe mode.
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.
Pressure switch 3 (I/C)Detects any malfunction in the input clutch hydraulic pressure. When it detects any mal-
function, it puts the system into fail-safe mode.
Pressure switch 5 (D/C)Detects any malfunction in the direct clutch hydraulic pressure. When it detects any mal-
function, it puts the system into fail-safe mode.
Pressure switch 6 (HLR/C)Detects any malfunction in the high and low reverse clutch hydraulic pressure. When it
detects any malfunction, it puts the system into fail-safe mode.

AT-44
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
l: NG X: OK
A/T 1st Engine Braking
• When there is an A/T first gear engine brake judgment malfunction, 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 set 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 1st and 2nd gear.
Input Clutch Solenoid
• If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4th gear 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 4th gear 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 5th gear; if the solenoid is OFF, 4th gear.
High and Low Reverse Clutch Solenoid
• If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4th gear to make driving possible.
Turbine Revolution Sensor 1 or 2
• The control is the same as if there were no turbine revolution sensors, 5th gear is prohibited.
How To Perform Trouble Diagnosis for Quick and Accurate RepairINFOID:0000000003532245
INTRODUCTION
The TCM receives a signal from the vehicle speed sensor, accelerator pedal position sensor (throttle position
sensor) or PNP switch and provides shift control or lock-up control via A/T solenoid valves.
The TCM also communicates with the ECM by means of a signal
sent from sensing elements used with the OBD-related parts of the
A/T system for malfunction-diagnostic purposes. The TCM is capa-
ble of diagnosing malfunctioning parts while the ECM can store mal-
functions in its memory.
Input and output signals must always be correct and stable in the
operation of the A/T system. The A/T system must be in good oper-
ating condition and be free of valve seizure, solenoid valve malfunc-
tion, etc.
Gear positionATF pressure switch output
Fail-safe
functionClutch pressure output pattern after fail-safe func-
tion
SW3
(I/C)SW6
(HLR/
C)SW5
(D/C)SW1
(FR/B)SW2
(LC/B)I/C HLR/C D/C FR/B LC/B L/U
A/T interlock
coupling pat-
tern3rd – X X – lHeld in
2nd gearOFF OFF ON OFF OFF OFF
4th – X X –lHeld in
2nd gearOFF OFF ON OFF OFF OFF
5th X X – XlHeld in
2nd gearOFF OFF ON OFF OFF OFF
SAT631IB

TROUBLE DIAGNOSIS
AT-47
< SERVICE INFORMATION >
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Customer name MR/MS Model & Year VIN
Trans. Model Engine Mileage
Malfunction Date Manuf. Date In Service Date
Frequencyo Continuouso Intermittent ( times a day)
Symptomso Vehicle does not move. (o Any positiono Particular position)
o No up-shift (o 1st → 2ndo 2nd → 3rdo 3rd → 4th o 4th → 5th)
o No down-shift (o 5th → 4th o 4th → 3rdo 3rd → 2ndo 2nd → 1st)
o Lock-up malfunction
o Shift point too high or too low.
o Shift shock or slip (o N → Do Lock-upo Any drive position)
o Noise or vibration
o No kick down
o No pattern select
o Others
()
Malfunction indicator lamp (MIL)o Continuously lito Not lit
1o Read the item on cautions concerning fail-safe and understand the customer's complaint.AT- 4 3
2o ATF inspection
AT- 5 1o Leak (Repair leak location.)
o Sta te
o Amount
3o Stall test and line pressure test
AT- 5 1
, AT-
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o Stall test
o Torque converter one-way clutch
o Front brake
o High and low reverse clutch
o Low coast brake
o Forward brake
o Reverse brake
o Forward one-way clutcho 1st one-way clutch
o 3rd one-way clutch
o Engine
o Line pressure low
o Except for input clutch and direct
clutch, clutches and brakes OK
o Line pressure inspection - Suspected part:

AT-52
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
Fluid Condition Check
Inspect the fluid condition.
STALL TEST
Stall Test Procedure
1. Inspect the amount of engine oil. Replenish the engine oil if necessary.
2. Drive for about 10 minutes to warm up the vehicle so that the A/
T fluid temperature is 50 to 80°C (122 to 176°F). Inspect the
amount of ATF. Replenish if necessary.
3. Securely engage the parking brake so that the tires do not turn.
4. Engine start, apply foot brake, and place selector lever in “D”
position.
5. While holding down the foot brake, gradually press down the
accelerator pedal.
6. Quickly read off the stall speed, then quickly remove your foot
from the accelerator pedal.
CAUTION:
Do not hold down the accelerator pedal for more than 5 sec-
onds during this test.
7. Move the selector lever to the “N” position.
8. Cool down the ATF.
CAUTION:
Run the engine at idle for at least one minute.
Fluid condition Conceivable Cause Required Operation
Varnished (viscous
varnish state)Clutch, brake
scorchedReplace the ATF and check the A/T
main unit and the vehicle for mal-
functions (wire harnesses, cooler
pipes, etc.)
Milky white or
cloudyWater in the fluidReplace the ATF and check for plac-
es where water is getting in.
Large amount of
metal powder mixed
inUnusual wear of
sliding parts within
A/TReplace the ATF and check for im-
proper operation of the A/T.
SAT638A
SAT647B
SCIA1224E
Stall speed: 2,500 - 2,800 rpm
SAT514G

TROUBLE DIAGNOSIS
AT-53
< SERVICE INFORMATION >
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O: Stall speed within standard value position
H: Stall speed higher than standard value
L: Stall speed lower than standard value
Stall test standard value position
LINE PRESSURE TEST
Line Pressure Test Port
Line Pressure Test Procedure
1. Inspect the amount of engine oil and replenish if necessary.
2. Drive the car for about 10 minutes to warm it up so that the ATF reaches in range of 50 to 80°C (122 to
176°F), then inspect the amount of ATF and replenish if necessary.
NOTE:
The automatic fluid temperature rises in range of 50 to 80°C (122 to 176°F) during 10 minutes of
driving.
3. After warming up remove the oil pressure detection plug and
install the oil pressure gauge [ST2505S001(J-34301-C)].
CAUTION:
When using the oil pressure gauge, be sure to use the O-
ring attached to the oil pressure detection plug.
Selector lever position
Expected problem location
DR
Stall rotation HO• Forward brake
• Forward one-way clutch
• 1st one-way clutch
• 3rd one-way clutch
O H • Reverse brake
L L • Engine and torque converter one-way clutch
H H • Line pressure low
Does not shift-up D position 1 → 2 Slipping in 2nd, 3rd, 4th gears Direct clutch slippage
Does not shift-up D position 2 → 3 Slipping in 3rd, 4th, 5th gears High and low reverse clutch slippage
Does not shift-up D position 3 → 4 Slipping in 4th, 5th gears Input clutch slippage
Does not shift-up D position 4 → 5 Slipping in 5th gear Front brake slippage
SCIA2187E
SCIA5309E

TROUBLE DIAGNOSIS
AT-61
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No. Items Symptom Condition Diagnostic ItemReference
page
1
Shift
ShockLarge shock. (“N” →“
D” position)
Refer to AT- 1 7 0 ,
"Large Shock ("N" to
"D" Position)".ON vehicle1. Engine idle speedEC-75
2. Engine speed signalAT-109
3. Accelerator pedal position sensorAT- 11 7
4. Control cable adjustmentAT-208
5. ATF temperature sensorAT- 11 9
6. ATF pressure switch 1 and front brake solenoid valveAT- 1 5 0,
AT-134
7. CAN communication lineAT- 9 1
8. Fluid level and stateAT- 5 1
9. Line pressure testAT- 5 1
10. Control valve with TCMAT-210
OFF vehicle11. Forward brake (Parts behind drum support is impossible
to perform inspection by disassembly. Refer to AT- 1 9, AT- 2 0.)AT-240
2Shock is too large
when changing D1 →
D
2.ON vehicle1. Accelerator pedal position sensorAT- 11 7
2. Control cable adjustmentAT-208
3. ATF pressure switch 5 and direct clutch solenoid valveAT- 1 5 4,
AT-138
4. CAN communication lineAT- 9 1
5. Engine speed signalAT-109
6. Turbine revolution sensorAT-103
7. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT-124
8. Fluid level and stateAT- 5 1
9. Control valve with TCMAT-210
OFF vehicle 10. Direct clutchAT-274
3Shock is too large
when changing D2 →
D
3.ON vehicle1. Accelerator pedal position sensorAT- 11 7
2. Control cable adjustmentAT-208
3. ATF pressure switch 6, high and low reverse clutch sole-
noid valveAT- 1 5 6,
AT-142
4. CAN communication lineAT- 9 1
5. Engine speed signalAT-109
6. Turbine revolution sensorAT-103
7. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT-124
8. Fluid level and stateAT- 5 1
9. Control valve with TCMAT-210
OFF vehicle 10. High and low reverse clutchAT-272

AT-62
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
4
Shift
ShockShock is too large
when changing D3 →
D
4.ON vehicle1. Accelerator pedal position sensorAT- 11 7
2. Control cable adjustmentAT- 2 0 8
3. ATF pressure switch 3 and input clutch solenoid valveAT- 1 5 2,
AT- 1 3 0
4. CAN communication lineAT- 9 1
5. Engine speed signalAT- 1 0 9
6. Turbine revolution sensorAT- 1 0 3
7. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT- 1 2 4
8. Fluid level and stateAT- 5 1
9. Control valve with TCMAT- 2 1 0
OFF vehicle 10. Input clutchAT- 2 6 2
5Shock is too large
when changing D4 →
D
5.ON vehicle1. Accelerator pedal position sensorAT- 11 7
2. Control cable adjustmentAT- 2 0 8
3. ATF pressure switch 1 and front brake solenoid valveAT- 1 5 0,
AT- 1 3 4

4. CAN communication lineAT- 9 1
5. Engine speed signalAT- 1 0 9
6. Turbine revolution sensorAT- 1 0 3
7. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT- 1 2 4
8. Fluid level and stateAT- 5 1
9. Control valve with TCMAT- 2 1 0
OFF vehicle10. Front brake (brake band)AT- 2 2 811. Input clutchAT- 2 6 2
6Shock is too large for
downshift when accel-
erator pedal is
pressed.ON vehicle1. Accelerator pedal position sensorAT- 11 7
2. Control cable adjustmentAT- 2 0 8
3. CAN communication lineAT- 9 1
4. Engine speed signalAT- 1 0 9
5. Turbine revolution sensorAT- 1 0 3
6. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT- 1 2 4
7. Fluid level and stateAT- 5 1
8. Control valve with TCMAT- 2 1 0
OFF vehicle9. Front brake (brake band)AT- 2 2 8
10. Input clutchAT- 2 6 2
11. High and low reverse clutchAT- 2 7 2AT-
272
12. Direct clutchAT- 2 7 4
No. Items Symptom Condition Diagnostic ItemReference
page