2008 INFINITI QX56 ESP

DIAGNOSIS AND REPAIR WORKFLOWTM-5
< BASIC INSPECTION >
CEF
G H
I
J
K L
M A
B
TM
N
O P
BASIC INSPECTION
DIAGNOSIS AND REPAIR WORKFLOW
Work FlowINFOID:0000000001603985
INTRODUCTION
The TCM receives a signal from the output speed sensor, accelera-
tor pedal position sensor (throttle position sensor) or transmission
range switch. Then provides shift c ontrol 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 wit h 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. T he A/T system must be in good oper-
ating condition and be free of valve seizure, solenoid valve malfunc-
tion, etc.
It is much more difficult to diagnose an error that occurs intermit-
tently rather than continuously. Most intermittent errors are caused
by poor electric connections or impr oper wiring. In this case, careful
checking of suspected circuits may help prevent the replacement of
good parts.
A visual check only may not find t he cause of the errors. A road test
with CONSULT-III (or GST) or a circuit tester connected should be
performed. Follow the “DETAILED FLOW”.
Before undertaking actual checks, take a few minutes to talk with a
customer who approaches with a driveability complaint. The cus-
tomer can supply good information about such errors, especially
intermittent ones. Find out what symptoms are present and under
what conditions they occur. A “Diagnostic work sheet” as shown on
the example (Refer to TM-6
) should be used.
Start your diagnosis by looking for “conventional” errors first. This will
help troubleshoot driveability errors on an electronically controlled
engine vehicle.
Also check related Service bulletins.
DETAILED FLOW
1.COLLECT THE INFORMATION FROM THE CUSTOMER
Get the detailed information from the customer about the symptom (the condition and the environment when
the incident/malfunction occurred) us ing diagnosis worksheet. Refer to TM-6, "
Diagnostic Work Sheet".
>> GO TO 2.
2.CHECK SYMPTOM 1
Check the following items based on the in formation obtained from the customer.
• Fail-safe. Refer to TM-114, "
Fail-Safe".
• A/T fluid inspection. Refer to TM-178, "
Checking the A/T Fluid (ATF)".
• Stall test. Refer to TM-185, "
Inspection and Judgment".
• Line pressure test. Refer to TM-187, "
Inspection and Judgment".
SAT631IB
SAT632I
SEF234G
Revision: March 2010 2008 QX56

TM-20
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
TCM Function
INFOID:0000000001603990
The function of the TCM is to:
• Receive input signals sent from various switches and sensors.
• Determine required line pressure, shifting poi nt, lock-up operation, and engine brake operation.
• Send required output signals to the respective solenoids.
CONTROL SYSTEM OUTLINE
The automatic transmission senses vehicle operating conditions through vari ous sensors or signals. It always
controls the optimum shift position and reduces shifting and lock-up shocks.
1. Front brake 2. Input clutch3. 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 gear12. Input shaft
13. Mid internal gear 14. Front internal gear15. Rear carrier
16. Rear sun gear 17. Mid sun gear18. Front carrier
19. Mid carrier 20. Rear internal gear21. Output shaft
22. Parking gear 23. Parking pawl
SCIA1519E
Revision: March 2010 2008 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:0000000001603994
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: March 2010 2008 QX56

TM-30
< FUNCTION DIAGNOSIS >
ON BOARD DIAGNOSTIC (OBD) SYSTEM
ON BOARD DIAGNOSTIC (OBD) SYSTEM
IntroductionINFOID:0000000001604002
The A/T system has two self-diagnostic systems.
The first is the emission-related on board diagnostic syst em (OBD-II) performed by the TCM in combination
with the ECM. The malfunction is indicated by the MI L (malfunction indicator lamp) and is stored as a DTC in
the ECM memory but not the TCM memory.
The second is the TCM original self-diagnosis indicated by the A/T CHECK indicator lamp. The malfunction is
stored in the TCM memory. The detected items are ov erlapped with OBD-II self-diagnostic items. For detail,
refer to TM-32, "
CONSULT-III Function (TRANSMISSION)".
OBD-II Function for A/T SystemINFOID:0000000001604003
The ECM provides emission-related on board diagnostic (O BD-II) functions for the A/T system. One function
is to receive a signal from the TCM used with OBD-relat ed parts of the A/T system. The signal is sent to the
ECM when a malfunction occurs in the corresponding OBD-re lated part. The other function is to indicate a
diagnostic result by means of the MIL (malfunction indi cator lamp) on the instrument panel. Sensors, switches
and solenoid valves are used as sensing elements.
The MIL automatically illuminates in One or Two Trip Detection Logic when a malfunction is sensed in relation
to A/T system parts.
One or Two Trip Detection Logic of OBD-IIINFOID:0000000001604004
ONE TRIP DETECTION LOGIC
If a malfunction is sensed during the first test drive, the MIL will illuminate and the malfunction will be stored in
the ECM memory as a DTC. The TCM is not provided with such a memory function.
TWO TRIP DETECTION LOGIC
When a malfunction is sensed during the first test drive, it is stored in the ECM memory as a 1st trip DTC
(diagnostic trouble code) or 1st trip freeze frame data. At this point, the MIL will not illuminate. — 1st Trip
If the same malfunction as that experienced during the fi rst test drive is sensed during the second test drive,
the MIL will illuminate. — 2nd Trip
The “Trip” in the “One or Two Trip Detection Logic” means a driving mode in which self-diagnosis is performed
during vehicle operation.
OBD-II Diagnostic Trouble Code (DTC)INFOID:0000000001604005
HOW TO READ DTC AND 1ST TRIP DTC
DTC and 1st trip DTC can be read by the following methods.
( with CONSULT-III or GST) CONSULT-III or GST (Generic Scan Tool) Examples: P0705, P0720 etc.
These DTC are prescribed by SAE J2012.
(CONSULT-III also displays the malfunctioning component or system.)
• 1st trip DTC No. is the same as DTC No.
• Output of the diagnostic troubl e code indicates that the indicated circuit has a malfunction. How-
ever, in case of the Mode II and GST, they do not indicate whether the malfunction is still occurring or
occurred in the past and returned to normal.
CONSULT-III can identify them as shown below, therefore, CONSULT-III (if available) is recom-
mended.
Freeze Frame Data and 1st Trip Freeze Frame Data
The ECM has a memory function, which stores the driv ing condition such as fuel system status, calculated
load value, engine coolant temperatur e, short term fuel trim, long term fuel trim, engine speed and vehicle
speed at the moment the ECM detects a malfunction.
Data which are stored in the ECM memory, along with the 1st trip DTC, are called 1st trip freeze frame data,
and the data, stored together with the DTC data, are called freeze frame data and displayed on CONSULT-III
or GST. The 1st trip freeze frame data can only be disp layed on the CONSULT-III screen, not on the GST. For
detail, refer to TM-30
.
Only one set of freeze frame data (either 1st trip freeze frame data of freeze frame data) can be stored in the
ECM. 1st trip freeze frame data is stored in the ECM memory along with the 1st trip DTC. There is no priority
for 1st trip freeze frame data and it is updated each time a different 1st trip DTC is detected. However, once
freeze frame data (2nd trip detection/MIL on) is stored in the ECM memory, 1st trip freeze frame data is no
Revision: March 2010 2008 QX56

TM-48
< COMPONENT DIAGNOSIS >
P0720 OUTPUT SPEED SENSOR
P0720 OUTPUT SPEED SENSOR
DescriptionINFOID:0000000001604038
The output speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse sig-
nal. The pulse signal is sent to the TCM which converts it into vehicle speed.
CONSULT-III Reference Value in Data Monitor ModeINFOID:0000000001604039
On Board Diagn osis LogicINFOID:0000000001604040
• This is an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0720” with CONSULT-III is detected under the following conditions.
- When TCM does not receive the proper voltage signal from the sensor.
- After ignition switch is turned “ON”, irregular signal input from vehicle speed signal before the vehicle starts
moving.
Possible CauseINFOID:0000000001604041
• Harness or connectors (The sensor circuit is open or shorted.)
• Output speed sensor
• Output speed signal
DTC Confirmation ProcedureINFOID:0000000001604042
CAUTION:
• Always drive vehicle at a safe speed.
• Be careful not to rev engine into the red zone on the tachometer.
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 proc edure to confirm the malfunction is eliminated.
WITH CONSULT-III
1. Turn ignition switch “ON”. (Do not start engine.)
2. Select “DATA MONITOR” mode for “TRANSMISSION” with CONSULT-III.
3. Drive vehicle and check for an increase of “VHCL/S SE·A/T” value in response to “VHCL/S SE·MTR”
value.
If the check result is NG, go to TM-49, "
Diagnosis Procedure".
If the check result is OK, go to following step.
4. Select “DATA MONITOR” mode for “ENGINE” with CONSULT-III.
5. Start engine and maintain the following conditions for at least 5 consecutive seconds.
VHCL SPEED SE: 30 km/h (19 MPH) or more
THRTL POS SEN: More than 1.0/8
Selector lever: “D” position
Driving location: Driving the vehicle uphill (increased engine load) will help maintain the driving
conditions required for this test.
If the check result is NG, go to TM-49, "
Diagnosis Procedure".
If the check result is OK, go to following step.
6. Maintain the following conditions for at least 5 consecutive seconds.
ENGINE SPEED: 3,500 rpm or more
THRTL POS SEN: More than 1.0/8
Selector lever: “D” position
Driving location: Driving the vehicle uphill (increased engine load) will help maintain the driving
conditions required for this test.
If the check result is NG, go to TM-49, "
Diagnosis Procedure".
Item name Condition Display value (km/h)
VHCL/S SE·A/T During driving Approximately matches the speedometer reading.
Revision: March 2010 2008 QX56

P0725 ENGINE SPEEDTM-51
< COMPONENT DIAGNOSIS >
CEF
G H
I
J
K L
M A
B
TM
N
O P
P0725 ENGINE SPEED
DescriptionINFOID:0000000001604044
The engine speed signal is sent from the ECM to the TCM.
CONSULT-III Reference Val ue in Data Monitor ModeINFOID:0000000001604045
On Board Diagnosis LogicINFOID:0000000001604046
• This is not an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0725” with CONSULT-III is det ected when TCM does not receive the ignition sig-
nal from ECM during engine cranking or running.
Possible CauseINFOID:0000000001604047
Harness or connectors
(The ECM to the TCM circuit is open or shorted.)
DTC Confirmation ProcedureINFOID:0000000001604048
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” and select “DATA MO NITOR” mode for “TRANSMISSION” with CONSULT-III.
2. Start engine and maintain the following conditions for at least 10 consecutive seconds. VHCL SPEED SE: 10 km/h (6 MPH) or more
ACCELE POSI: More than 1/8
Selector lever: “D” position
3. If DTC is detected, go to TM-51, "
Diagnosis Procedure".
Diagnosis ProcedureINFOID:0000000001604049
1.CHECK CAN COMMUNICATION LINE
Perform the self-diagnosis. Refer to TM-32, "
CONSULT-III Function (TRANSMISSION)".
Is a malfunction in the CAN communication indicated in the results?
YES >> Check CAN communication line. Refer to TM-38.
NO >> GO TO 2.
2.CHECK DTC WITH TCM
With CONSULT-III
1. Start engine.
2. Select “ECU INPUT SIGNALS” in “DATA MONITO R” mode for “TRANSMISSION” with CONSULT-III.
3. While monitoring engine speed, check for engine speed change corresponding to \
wide-open throttle posi-
tion signal.
OK or NG
OK >> GO TO 3.
Item name Condition Display value (rpm)
ENGINE SPEED Engine running Closely matches the tachometer reading.
Item name Condition Display value (rpm)
ENGINE SPEED Engine running Closely matches the tachometer reading.
Revision: March 2010 2008 QX56

P0740 TORQUE CONVERTERTM-63
< COMPONENT DIAGNOSIS >
CEF
G H
I
J
K L
M A
B
TM
N
O P
P0740 TORQUE CONVERTER
DescriptionINFOID:0000000001604075
• The torque converter clutch solenoid valve is activated, with the gear in D4, D5 by the TCM in response to
signals sent from the input speed s ensor and accelerator pedal position s ensor (throttle 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:0000000001604076
On Board Diagnosis LogicINFOID:0000000001604077
• This is an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0740” with 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:0000000001604078
• Torque converter clutch solenoid valve
• Harness or connectors
(The solenoid circuit is open or shorted.)
DTC Confirmation ProcedureINFOID:0000000001604079
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 SPEED SE: 80 km/h (50 MPH) or more
ACCELE POS: 0.5/8 - 1.0/8
SELECTOR LEVER: “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-63, "
Diagnosis Procedure".
WITH GST
Follow the procedure “With CONSULT-III”.
Diagnosis ProcedureINFOID:0000000001604080
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.
3. Start engine.
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: March 2010 2008 QX56

P0745 PRESSURE CONTROL SOLENOID ATM-67
< COMPONENT DIAGNOSIS >
CEF
G H
I
J
K L
M A
B
TM
N
O P
P0745 PRESSURE CONTROL SOLENOID A
DescriptionINFOID:0000000001604087
The line pressure solenoid valve regulates the oil pum p discharge pressure to suit the driving condition in
response to a signal sent from the TCM.
The line pressure duty cycle value is not consistent when the closed throttle position signal is “ON”.
To confirm the line pressure duty cycle at low pressu re, the accelerator (throttle) should be open until
the closed throttle posi tion signal is “OFF”.
CONSULT-III Reference Val ue in Data Monitor ModeINFOID:0000000001604088
On Board Diagnosis LogicINFOID:0000000001604089
• This is an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0745” with 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:0000000001604090
• Harness or connectors
(The solenoid circuit is open or shorted.)
• Line pressure solenoid valve
DTC Confirmation ProcedureINFOID:0000000001604091
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” and select “DATA MONITOR” mode for “ENGINE” with CONSULT-III.
2. Engine start and wait at least 5 second.
3. If DTC is detected, go to TM-67, "
Diagnosis Procedure".
WITH GST
Follow the procedure “With CONSULT-III”.
Diagnosis ProcedureINFOID:0000000001604092
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.
3. Start the engine.
4. Read out the value of “LINE PRES SOL” while driving.
OK or NG
OK >> GO TO 4.
NG >> GO TO 2.
2.CHECK TCM POWER SUPPLY AND GROUND CIRCUIT
Item name Condition Display value (Approx.)
LINE PRES SOL During driving0.2 - 0.6 A
Item nameCondition Display value (Approx.)
LINE PRES SOL During driving 0.2 - 0.6 A
Revision: March 2010 2008 QX56