2007 INFINITI QX56 transmission

AT-36
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
*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 ControlINFOID:0000000003532235
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.
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 5 4 4 3 2
Lock-up×–×××
Slip lock-up××–––
PCIA0014E

TROUBLE DIAGNOSIS
AT-43
< SERVICE INFORMATION >
D
E
F
G
H
I
J
K
L
MA
B
AT
N
O
P
TROUBLE DIAGNOSIS
DTC Inspection Priority ChartINFOID:0000000003532243
If some DTCs are displayed at the same time, perform inspections one by one based on the following priority
chart.
NOTE:
If DTC U1000 is displayed with other DTCs, first perform the trouble diagnosis for DTC U1000. Refer to
AT- 9 1
.
Fail-SafeINFOID:0000000003532244
The TCM has an electrical fail-safe mode. This mode makes it possible to operate even if there is an error in a
main electronic control input/output signal circuit. In fail-safe mode the transmission is fixed in 2nd, 4th or 5th
(depending on the breakdown position), so the customer should feel “slipping” or “poor acceleration”.
Even when the electronic circuits are normal, under special conditions (for example, when slamming on the
brake with the wheels spinning drastically and stopping the 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 vehicle has returned to normal, so handle according to the
“diagnostics flow” (Refer to AT-44, "
How To Perform Trouble Diagnosis for Quick and Accurate Repair").
FAIL-SAFE FUNCTION
If any malfunction occurs in a sensor or solenoid, this function controls the A/T to mark driving possible.
Vehicle Speed Sensor
• Signals are input from two systems - from vehicle speed sensor A/T (revolution sensor) installed on the
transmission and from combination meter so normal driving is possible even if there is a malfunction in one
of the systems. And if vehicle speed sensor A/T (revolution sensor) has unusual cases, 5th gear is prohib-
ited.
Accelerator Pedal 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.
PNP Switch
• In the unlikely event that a malfunction signal enters the 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.)
A/T Interlock
• If there is an A/T interlock judgment malfunction, the transmission is fixed in 2nd gear to make driving possi-
ble.
NOTE:
When the vehicle is driven fixed in 2nd gear, a turbine revolution sensor malfunction is displayed,
but this is not a turbine revolution sensor malfunction.
• When the coupling pattern below is detected, the fail-safe action corresponding to the pattern is performed.
A/T INTERLOCK COUPLING PATTERN TABLE
Priority Detected items (DTC)
1 U1000 CAN communication line
2 Except above

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-51
< SERVICE INFORMATION >
D
E
F
G
H
I
J
K
L
MA
B
AT
N
O
P
Circuit DiagramINFOID:0000000003532247
Inspections Before Trouble DiagnosisINFOID:0000000003532248
A/T FLUID CHECK
Fluid Leakage and Fluid Level Check
• Inspect for fluid leakage and check the fluid level. Refer to AT-13, "Changing Automatic Transmission Fluid
(ATF)".
BCWA0496E

AT-56
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
3. Turn ignition switch to “START” position.
Does the engine start in either position?
YES >> Stop the road test and go to AT-168, "Engine Cannot Be Started in "P" or "N" Position".
NO >> GO TO 3.
3.CHECK “P” POSITION FUNCTIONS
1. Move selector lever to “P” position.
2. Turn ignition switch to “OFF” position.
3. Release the parking brake.
4. Push the vehicle forward or backward.
5. Engage the parking brake.
When you push the vehicle with disengaging the parking brake, does it move?
YES >> Enter a check mark at “In “P” Position Vehicle Moves When Pushed” on the diagnostics work-
sheet, then continue the road test.
NO >> GO TO 4.
4.CHECK “N” POSITION FUNCTIONS
1. Start the engine.
2. Move selector lever to “N” position.
3. Release the parking brake.
Does vehicle move forward or backward?
YES >> Enter a check mark at “In “N” Position Vehicle Moves” on the diagnostics worksheet, then con-
tinue the road test.
NO >> GO TO 5.
5.CHECK SHIFT SHOCK
1. Engage the brake.
2. Move selector lever to “D” position.
When the transmission is shifted from
“N” to “D”, is there an excessive shock?
YES >> Enter a check mark at “Large Shock ("N" to "D" Position) on the diagnostics worksheet, then con-
tinue the road test.
NO >> GO TO 6.
6.CHECK “R” POSITION FUNCTIONS
1. Engage the brake.
2. Move selector lever to “R” position.
3. Release the brake for 4 to 5 seconds.
Does the vehicle creep backward?
YES >> GO TO 7.
NO >> Enter a check mark at “Vehicle Does Not Creep Backward In "R" Position” on the diagnostics
worksheet, then continue the road test.
7.CHECK “D” POSITION FUNCTIONS
Inspect whether the vehicle creeps forward when the transmission is put into the “D” position.
Does the vehicle creep forward in the
“D” positions?
YES >> Go to AT-56, "Cruise Test - Part 1", AT-58, "Cruise Test - Part 2", and AT-59, "Cruise Test - Part 3".
NO >> Enter a check mark at “Vehicle Does Not Creep Forward in "D" Position” on the diagnostics work-
sheet, then continue the road test.
Cruise Test - Part 1INFOID:0000000003532251
1.CHECK STARTING OUT FROM D1
1. Drive the vehicle for about 10 minutes to warm up the engine oil and ATF.
Appropriate temperature for the ATF: 50 - 80°C (122 - 176°F)
2. Park the vehicle on a level surface.
3. Move selector lever to “P” position.
4. Start the engine.
5. Move selector lever to “D” position.

AT-58
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
Does it lock-up?
YES >> GO TO 7.
NO >> Enter a check mark at “A/T Does Not Perform Lock-up” on the diagnostics worksheet, then con-
tinue the road test.
7.CHECK LOCK-UP HOLD
Does it maintain lock-up status?
YES >> GO TO 8.
NO >> Enter a check mark at “A/T Does Not Hold Lock-up Condition” on the diagnostics worksheet, then
continue the road test.
8.CHECK LOCK-UP RELEASE
Check lock-up cancellation by depressing brake pedal lightly to decelerate.
With CONSULT-II
Select “TCC SOLENOID 0.00A” with the “MAIN SIGNAL” mode for A/T.
Does lock-up cancel?
YES >> GO TO 9.
NO >> Enter a check mark at “Lock-up Is Not Released” on the diagnostics worksheet, then continue the
road test.
9.CHECK SHIFT-DOWN D5 → D4
Decelerate by pressing lightly on the brake pedal.
With CONSULT-II
Read the gear position and engine speed.
When the A/T shift-down D5
→ D4, does the engine speed drop smoothly back to idle?
YES >> 1. Stop the vehicle.
2. Go to Cruise test - Part 2 (Refer to AT- 5 8
).
NO >> Enter a check mark at “Engine Speed Does Not Return to Idle” on the diagnostics worksheet, then
continue the road test. Go to Cruise test - Part 2 (Refer to AT- 5 8
).
Cruise Test - Part 2INFOID:0000000003532252
1.CHECK STARTING FROM D1
1. Move selector lever the “D” position.
2. Accelerate at half throttle.
With CONSULT-II
Read the gear position.
Does it start from D1?
YES >> GO TO 2.
NO >> Enter a check mark at “Vehicle Cannot Be Started From D1” on the diagnostics worksheet, then
continue the road test.
2.CHECK SHIFT-UP D1 → D2
Press the accelerator pedal down all the way and inspect whether or not the transmission shifts up (D1 → D2)
at the correct speed.
• Refer to AT-59, "
Vehicle Speed When Shifting Gears".
With CONSULT-II
Read the gear position, throttle position and vehicle speed.
Does the A/T shift-up D1
→ D2 at the correct speed?
YES >> GO TO 3.
NO >> Enter a check mark at “Vehicle Does Not Shift: D1 → D2” on the diagnostics worksheet, then con-
tinue the road test.
3.CHECK SHIFT-UP D2 → D3
Press the accelerator pedal down all the way and inspect whether or not the transmission shifts up (D2 → D3)
at the correct speed.

TROUBLE DIAGNOSIS
AT-59
< SERVICE INFORMATION >
D
E
F
G
H
I
J
K
L
MA
B
AT
N
O
P
• Refer to AT-59, "Vehicle Speed When Shifting Gears".
With CONSULT-II
Read the gear position, throttle position and vehicle speed.
Does the A/T shift-up D2
→ D3 at the correct speed?
YES >> GO TO 4.
NO >> Enter a check mark at “Vehicle Does Not Shift: D2 → D3” on the diagnostics worksheet, then con-
tinue the road test.
4.CHECK SHIFT-UP D3 → D4 AND ENGINE BRAKE
When the transmission changes speed D3 → D4, return the accelerator pedal.
Does the A/T shift-up D3
→ D4 and apply the engine brake?
YES >> 1. Stop the vehicle.
2. See AT-59, "
Cruise Test - Part 3".
NO >> Enter a check mark at “Vehicle Does Not Shift: D3 → D4” on the diagnostics worksheet, then con-
tinue the road test.
Cruise Test - Part 3INFOID:0000000003532253
1.CHECK SHIFT-DOWN
During D
5 driving, move gear selector from D → 4 → 3 → 2 → 1.
With CONSULT-II
Read the gear position.
Is downshifting correctly performed?
YES >> GO TO 2.
NO >> Enter a check mark at “Vehicle does not shift” at the corresponding position (5th → 4th, 4th → 3rd,
3rd → 2nd, 2nd → 1st) on the diagnostics worksheet, then continue the road test.
2.CHECK ENGINE BRAKE
Does engine braking effectively reduce speed in 1
1 position?
YES >> 1. Stop the vehicle.
2. Carry out the self-diagnostics. Refer to AT-83, "
CONSULT-II Function (A/T)".
NO >> Enter a check mark at “Vehicle Does Not Decelerate By Engine Brake” on the diagnostics work-
sheet, then continue trouble diagnosis.
Vehicle Speed When Shifting GearsINFOID:0000000003532254
NORMAL MODE
• At half throttle, the accelerator opening is 4/8 of the full opening.
TOW MODE
Final
gear
ratioThrottle positionVehicle speed km/h (MPH)
D
1 →D2D2 →D3D3 →D4D4 →D5D5 →D4D4 →D3D3 →D2D2 →D1
2.937Full throttle 70 - 74
(44 - 46)112 - 120
(70 - 75)176 - 186
(110 - 116)249 - 259
(155 - 161)245 - 255
(152 - 159)166 - 176
(103 - 110)100 - 108
(62 - 67)43 - 47
(27 - 30)
Half throttle 46 - 50
(28 - 31)74 - 82
(46 - 51)103 - 113
(64 - 70)135 - 145
(84 - 90)109 - 119
(68 - 74)69 - 79
(43 - 49)44 - 52
(27 - 32)11 - 1 5
(7 - 10)
3.357Full throttle 61 - 65
(38 - 41)97 - 105
(61 - 66)153 - 163
(95 - 102)236 - 246
(147 - 153)232 - 242
(144 - 151)143 - 153
(89 - 95)87 - 95
(54 - 59)43 - 47
(27 - 29)
Half throttle 41 - 45
(26 - 28)66 - 74
(41 - 46)89 - 99
(56 - 62)11 7 - 1 2 7
(73 - 79)95 - 105
(59 - 65)59 - 69
(37 - 43)38 - 46
(24 - 29)11 - 1 5
(7 - 10)
Final
gear
ratioThrottle positionVehicle speed km/h (MPH)
D
1 →D2D2 →D3D3 →D4D4 →D5D5 →D4D4 →D3D3 →D2D2 →D1

TROUBLE DIAGNOSIS
AT-71
< SERVICE INFORMATION >
D
E
F
G
H
I
J
K
L
MA
B
AT
N
O
P
30
Slips/Will
Not en-
gageNo shock at all or the
clutch slips when vehi-
cle changes speed D4
→ D
5.ON vehicle1. Fluid level and stateAT- 5 1
2. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT-124
3. ATF pressure switch 1 and front brake solenoid valveAT- 1 5 0,
AT-134
4. ATF pressure switch 5 and direct clutch solenoid valveAT- 1 5 4,
AT-138
5. CAN communication lineAT- 9 1
6. Line pressure testAT- 5 1
7. Control valve with TCMAT-210
OFF vehicle8. Torque converterAT-240
9. Oil pump assemblyAT-258
10. Front brake (brake band)AT-240
11. Input clutchAT-262
12. Gear systemAT-228
13. High and low reverse clutchAT-272
31When you press the
accelerator pedal and
shift speed D5 → D4
the engine idles or the
transmission slips.ON vehicle1. Fluid level and stateAT- 5 1
2. Vehicle speed sensor A/T and vehicle speed sensor MTRAT- 1 0 5,
AT-124
3. ATF pressure switch 1 and front brake solenoid valveAT- 1 5 0,
AT-134
4. ATF pressure switch 5 and direct clutch solenoid valveAT- 1 5 4,
AT-138
5. CAN communication lineAT- 9 1
6. Line pressure testAT- 5 1
7. Control valve with TCMAT-210
OFF vehicle8. Torque converterAT-240
9. Oil pump assemblyAT-258
10. Input clutchAT-262
11. Gear systemAT-228
12. High and low reverse clutchAT-272
13. Direct clutchAT-274
No. Items Symptom Condition Diagnostic ItemReference
page