2004 INFINITI QX56 Back up

A/T CONTROL SYSTEM
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Line Pressure ControlUCS002C H

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.

This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the
pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the
driving state.
LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC
PATTERN

The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the
driving state.

In order to obtain the most appropriate line pressure characteristic to meet the current driving state, the
TCM controls the line pressure solenoid current valve and thus controls the line pressure.
Normal Control
Each clutch is adjusted to the necessary pressure to match the
engine drive force.
Back-up Control (Engine Brake)
When the select operation is performed during driving and the trans-
mission is shifted down, the line pressure is set according to the
vehicle speed.
PCIA0007E
PCIA0008E
PCIA0009E

A/T CONTROL SYSTEM
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Shift Change System Diagram
*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 ControlUCS002CJ
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.
PCIA0013E
Select lever D position 4 position 3 position 2 position
Gear position 5 4 4 3 2
Lock-up×–×××
Slip lock-up××–––
PCIA0014E

ON BOARD DIAGNOSTIC (OBD) SYSTEM
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1st trip freeze frame data

System readiness test (SRT) codes

Test values
HOW TO ERASE DTC (WITH CONSULT-II)

If a DTC is displayed for both ECM and TCM, it is necessary to be erased for both ECM and TCM.
1. If the ignition switch stays “ON” after repair work, be sure to turn ignition switch “OFF” once. Wait at least
10 seconds and then turn it “ON” (engine stopped) again.
2. Turn CONSULT-II “ON” and touch “A/T”.
3. Touch “SELF-DIAG RESULTS”.
4. Touch “ERASE”. (The DTC in the TCM will be erased.) Then touch “BACK” twice.
5. Touch “ENGINE”.
6. Touch “SELF-DIAG RESULTS”.
7. Touch “ERASE”. (The DTC in the ECM will be erased.)
HOW TO ERASE DTC (WITH GST)
1. If the ignition switch stays “ON” after repair work, be sure to turn ignition switch “OFF” once. Wait at least
10 seconds and then turn it “ON” (engine stopped) again.
2. Select Mode 4 with the Generic Scan Tool (GST). For details refer to EC-116, "
Generic Scan Tool (GST)
Function" .
HOW TO ERASE DTC (NO TOOLS)
1. Disconnect battery for 24 hours.
2. Reconnect battery.
SCIA5334E

TROUBLE DIAGNOSIS
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TROUBLE DIAGNOSISPFP:00004
DTC Inspection Priority ChartUCS002C R
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-1 03
.
Fail-SafeUCS002CS
The TCM has an electrical fail-safe mode. This mode makes it possible to operate even if there is a an error in
a main electronic control input/output signal circuit. In fail-safe mode the transmission is fixed in 2nd or 4th
(depending on the breakdown position), so the customer should feel “slipping” or “poor acceleration”. When
fail-safe mode is triggered, when the ignition switch is switched “ON”, the AT CHECK indicator lamp flashes for
about 8 seconds.
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. Also, the AT CHECK indicator lamp flashes for about 8 seconds once, then is cleared.
Therefore, the customer's vehicle has returned to normal, so handle according to the “diagnostics flow” (Refer
to AT-46, "
WORK FLOW" ).
FAI L-S AFE FUN CT ION
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
prohibited.
Accelerator Pedal Position Sensor

If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM accord-
ing to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow
systems, 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 accord-
ing to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow
systems, 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.)
Priority Detected items (DTC)
1 U1000 CAN communication line
2 Except above

AT-48
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
4❏ Perform all road tests and enter checks in required inspection items.AT-6 1
4-1.Check before engine is started
AT-6 2
❏ AT-191, "AT CHECK Indicator Lamp Does Not Come On" .
❏ Perform self-diagnostics Enter checks for detected items. AT- 9 3
❏ AT- 1 0 3 , "DTC U1000 CAN COMMUNICATION LINE"
❏ AT- 1 0 5 , "DTC P0615 START SIGNAL CIRCUIT"
❏ AT- 1 0 8 , "DTC P0700 TCM"
❏ AT- 1 0 9 , "DTC P0705 PARK/NEUTRAL POSITION SWITCH"
❏ AT- 11 2 , "DTC P0720 VEHICLE SPEED SENSOR A/T (REVOLUTION SENSOR)"
❏ AT- 11 5 , "DTC P0725 ENGINE SPEED SIGNAL"
❏ AT- 11 8 , "DTC P0740 TORQUE CONVERTER CLUTCH SOLENOID VALVE"
❏ AT- 1 2 1 , "DTC P0744 A/T TCC S/V FUNCTION (LOCK-UP)"
❏ AT- 1 2 4 , "DTC P0745 LINE PRESSURE SOLENOID VALVE"
❏ AT- 1 2 7 , "DTC P1702 TRANSMISSION CONTROL MODULE (RAM)"
❏ AT- 1 2 8 , "DTC P1703 TRANSMISSION CONTROL MODULE (ROM)"
❏ AT- 1 2 9 , "DTC P1705 THROTTLE POSITION SENSOR"
❏ AT- 1 3 1 , "DTC P1710 A/T FLUID TEMPERATURE SENSOR CIRCUIT"
❏ AT- 1 3 4 , "DTC P1716 TURBINE REVOLUTION SENSOR"
❏ AT- 1 3 6 , "DTC P1721 VEHICLE SPEED SENSOR MTR"
❏ AT- 1 3 9 , "DTC P1730 A/T INTERLOCK"
❏ AT- 1 4 2 , "DTC P1731 A/T 1ST ENGINE BRAKING"
❏ AT- 1 4 5 , "DTC P1752 INPUT CLUTCH SOLENOID VALVE"
❏ AT- 1 4 8 , "DTC P1754 INPUT CLUTCH SOLENOID VALVE FUNCTION"
❏ AT- 1 5 1 , "DTC P1757 FRONT BRAKE SOLENOID VALVE"
❏ AT- 1 5 4 , "DTC P1759 FRONT BRAKE SOLENOID VALVE FUNCTION"
❏ AT- 1 5 7 , "DTC P1762 DIRECT CLUTCH SOLENOID VALVE"
❏ AT- 1 6 0 , "DTC P1764 DIRECT CLUTCH SOLENOID VALVE FUNCTION"
❏ AT- 1 6 3 , "DTC P1767 HIGH AND LOW REVERSE CLUTCH SOLENOID VALVE"
❏ AT- 1 6 6 , "DTC P1769 HIGH AND LOW REVERSE CLUTCH SOLENOID VALVE
FUNCTION"
❏ AT- 1 6 9 , "DTC P1772 LOW COAST BRAKE SOLENOID VALVE"
❏ AT- 1 7 2 , "DTC P1774 LOW COAST BRAKE SOLENOID VALVE FUNCTION"
❏ AT- 1 7 5 , "DTC P1841 ATF PRESSURE SWITCH 1"
❏ AT- 1 7 8 , "DTC P1843 ATF PRESSURE SWITCH 3"
❏ AT- 1 8 1 , "DTC P1845 ATF PRESSURE SWITCH 5"
❏ AT- 1 8 4 , "DTC P1846 ATF PRESSURE SWITCH 6"
4-2.Idle inspection
AT-6 2
❏ AT-192, "Engine Cannot Be Started In “P” or “N” Position"
❏ AT-193, "In “P” Position, Vehicle Moves When Pushed"
❏ AT-194, "In “N” Position, Vehicle Moves"
❏ AT-195, "Large Shock (“N” to “D” Position)"
❏ AT-198, "Vehicle Does Not Creep Backward In “R” Position"
❏ AT-201, "Vehicle Does Not Creep Forward In “D” Position"
4-3.Driving tests
AT-6 3
Part 1
❏ AT-203, "
Vehicle Cannot Be Started From D1"
❏ AT-206, "A/T Does Not Shift: D1 → D2"
❏ AT-208, "A/T Does Not Shift: D2 → D3"
❏ AT-210, "A/T Does Not Shift: D3 → D4"
❏ AT-213, "A/T Does Not Shift: D4 → D5"
❏ AT-215, "A/T Does Not Perform Lock-up"
❏ AT-217, "A/T Does Not Hold Lock-up Condition"
❏ AT-219, "Lock-up Is Not Released"
❏ AT-220, "Engine Speed Does Not Return to Idle"

TROUBLE DIAGNOSIS
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TCM TERMINAL MEASUREMENT CHART
TCM terminals and data are reference value. Measured between each terminal and ground.
Te r m i n a l
No.Wire
colorItem Condition Data (Approx.)
1PPower supply
(Memory back-up)– Battery voltage
2PPower supply
(Memory back-up)– Battery voltage
3 W CAN-H – –
4VK-line (CONSULT-
II signal)The terminal is connected to the data link connector for CONSULT-II. –
5 B Ground – –
6Y/RPower supply– Battery voltage
–0V
7RBack-up lamp
relaySelector lever in “R” position. 0V
Selector lever in other positions. Battery voltage
8 R CAN-L – –
9 B/R Starter relaySelector lever in “N”,“ P” positions. Battery voltage
Selector lever in other positions. 0V
10 B Ground – –

AT-62
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
Check Before Engine is StartedUCS002CY
1. CHECK AT CHECK INDICATOR LAMP
1. Park vehicle on level surface.
2. Move selector lever to “P” position.
3. Turn ignition switch to “OFF” position and wait at least 10 seconds.
4. Turn ignition switch to “ON” position. (Do not start engine.)
Does AT CHECK indicator lamp light up for about 2 seconds?
YES >> GO TO 2.
NO >> Stop the road test and go to AT-191, "
AT CHECK Indicator Lamp Does Not Come On" .
2. CHECK AT CHECK INDICATOR LAMP
Does AT CHECK indicator lamp flash for about 8 seconds?
YES >> For TCM fail-safe mode, carry out self-diagnostics and record all NG items on the diagnostics
worksheet. Refer to AT - 9 3
.
NO >> 1. Turn ignition switch to “OFF” position.
2. Carry out the self-diagnostics and record all NG items on the diagnostics worksheet. Refer to
AT - 9 3
.
3. Go to AT- 6 2 , "
Check at Idle" .
Check at Idle UCS002CZ
1. CHECK STARTING THE ENGINE
1. Park vehicle on level surface.
2. Move selector lever to “P” or “N” position.
3. Turn ignition switch to “OFF” position.
4. Turn ignition switch to “START” position.
Does the engine start?
YES >> GO TO 2.
NO >> Stop the road test and go to AT-192, "
Engine Cannot Be Started In “P” or “N” Position" .
2. CHECK STARTING THE ENGINE
1. Turn ignition switch to “ON” position.
2. Move selector lever in “D”,“4”, “3”, “2”, “1” or “R” position.
3. Turn ignition switch to “START” position.
Does the engine start in either position?
YES >> Stop the road test and go to AT-192, "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 “Vehicle moves when pushed in “P” position” on the diagnostics worksheet,
then continue the road test.
NO >> GO TO 4.

TROUBLE DIAGNOSIS
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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 “Vehicle moves in “N” position” on the diagnostics worksheet, then continue
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 when shifted from N to D” on the diagnostics worksheet, then
continue the road test.
NO >> GO TO 6.
6. CHECK “R” POSITION FUNCTIONS
1. Engage the brake.
2. Move selector lever to “R” position.
3. Disengage 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 work-
sheet, then continue the road test.
7. CHECK “D” POSITION FUNCTIONS
Inspect whether the vehicle moves forward when the transmission is put into the “D” position.
Does the vehicle creep forward in the
“D” positions?
YES >> Go to AT- 6 3 , "Cruise Test - Part 1" , AT- 6 5 , "Cruise Test - Part 2" , and AT- 6 6 , "Cruise Test - Part
3" .
NO >> Enter a check mark at “Vehicle does not move forward in D positions” on the diagnostics work-
sheet, then continue the road test.
Cruise Test - Part 1UCS002D0
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.
6. Press the accelerator pedal about half way down to accelerate the vehicle.
With CONSULT-II
Read off the gear positions.
Starts 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.