INFINITI QX56 2008 Factory Service Manual

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

A/T CONTROL SYSTEMTM-25
< FUNCTION DIAGNOSIS >
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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:0000000001603995
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 controlled by the torque conver ter 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 position4 position 3 position 2 position
G ear p osit io n 54432
Lock-up ×– ×××
Slip lock-up ××–––
PCIA0014E
Revision: March 2010 2008 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 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 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:0000000001603996
• 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:0000000001603997
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: March 2010
2008 QX56

A/T CONTROL SYSTEMTM-27
< FUNCTION DIAGNOSIS >
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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 gear 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: March 2010
2008 QX56

TM-28
< FUNCTION DIAGNOSIS >
A/T CONTROL SYSTEM
Component Parts Location
INFOID:0000000001604000
AWDIA0837GB
Revision: March 2010 2008 QX56

A/T SHIFT LOCK SYSTEMTM-29
< FUNCTION DIAGNOSIS >
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A/T SHIFT LOCK SYSTEM
System DescriptionINFOID:0000000001696150
• The selector lever cannot be shifted from “P” (Park) unless the brake pedal is applied and the ignition knob switch is turned to the “ON” position.
• The ignition knob switch cannot be returned to the “OFF” position unless the selector lever is placed in “P”
(Park).
• The shift lock mechanism is controlled by t he ON-OFF operation of the shift lock solenoid.
• The key switch and ignition knob switch lock mechanism is controlled by the ON-OFF operation of the key
lock solenoid.
Component Parts LocationINFOID:0000000001696151
1. Emergency lever 2. Key lock solenoid3. Ignition knob switch
4. Shift lock control unit 5. Shift lock solenoid6. Detent switch
7. Shift lock release 8. Stop lamp switch
AWDIA0706ZZ
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

ON BOARD DIAGNOSTIC (OBD) SYSTEMTM-31
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longer stored. Remember, only one set of freeze frame data can be stored in the ECM. The ECM has the fol-
lowing priorities to update the data.
Both 1st trip freeze frame data and freeze frame data (along with the DTC) are cleared when the ECM mem-
ory is erased.
HOW TO ERASE DTC
The diagnostic trouble code can be erased by CONSULT- III, GST or ECM DIAGNOSTIC TEST MODE as
described following.
• If the battery cable is disconnected, the diagnostic trouble code will be lost within 24 hours.
• When you erase the DTC, using CONSULT-III or GS T is easier and quicker than switching the mode
selector on the ECM.
The following emission-related diagnostic information is cleared from the ECM memory when erasing DTC
related to OBD-II. For details, refer to EC-42, "
Emission-related Diagnostic Information".
• Diagnostic trouble codes (DTC)
• 1st trip diagnostic trouble codes (1st trip DTC)
• Freeze frame data
• 1st trip freeze frame data
• System readiness test (SRT) codes
• Test values
HOW TO ERASE DTC (WITH CONSULT-III)
1. The emission related diagnostic information in the TCM and ECM can be er\
ased by selectioning "ALL
ERASE" in the "Description" of "F INAL CHECK" mode with CONSULT-III.
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-72, "
Generic Scan Tool (GST)
Function".
HOW TO ERASE DTC (NO TOOLS)
1. Disconnect battery for 24 hours.
2. Reconnect battery.
Malfunction Indicator Lamp (MIL)INFOID:0000000001604006
DESCRIPTION
The MIL is located on the instrument panel.
1. The MIL will light up when the ignition switch is turned “ON” with-
out the engine running. This is a bulb check.
• If the MIL does not light up, refer to EC-55, "
Malfunction Indicator
Lamp (MIL)".
2. When the engine is start ed, the MIL should go off.
If the MIL remains on, the on board diagnostic system has
detected an engine system malfunction.
Priority Items
1 Freeze frame data Misfire — DTC: P0300 - P0306 Fuel Injection System Function — DTC: P0171, P0172, P0174, P0175
2 Except the above items (Includes A/T related items)
3 1st trip freeze frame data
SEF217U
Revision: March 2010 2008 QX56

TM-32
< FUNCTION DIAGNOSIS >
DIAGNOSIS SYSTEM (TCM)
DIAGNOSIS SYSTEM (TCM)
CONSULT-III Function (TRANSMISSION)INFOID:0000000001604007
CONSULT-III can display each diagnostic item us ing the diagnostic test modes shown following.
SELF-DIAGNOSTIC RESULT MODE
Operation Procedure
After performing SELF-DIAGNOSTIC RESULT MO DE, place check marks for results on the TM-6, "Diagnostic
Work Sheet". Reference pages are provided following the items.
Display Items List
X: Applicable, —: Not applicable
TCM diagnostic mode Description
WORK SUPPORT Supports inspections and adjustments. Commands are transmitted to the TCM for setting the status
suitable for required operation, input/output signals are received from the TCM and received data is
displayed.
SELF-DIAG RESULTS Displays TCM self-diagnosis results.
DATA MONITOR Displays TCM input/output data in real time.
CAN DIAG SUPPORT MNTR The result of transmit/receive diagnosis of CAN communication can be read.
ACTIVE TEST Operation of electrical loads can be checked by sending drive signal to them.
FUNCTION TEST Conducted by CONSULT-III instead of a technici an to determine whether each system is “OK” or “NG”.
ECU PART NUMBER TCM part number can be read.
Items (CONSULT-III screen terms) Malfunction is detected when... TCM self-di-
agnosis OBD-II (DTC)
Reference page
“TRANSMIS-
SION” with
CONSULT-III MIL indicator
lamp*1, “EN-
GINE” with
CONSULT-III or GST
CAN COMM CIRCUIT • When a malfunction is detected in CAN communica-
tions U1000 U1000
TM-38
STARTER RELAY• If this signal is ON other than in P or N position, this is
judged to be a malfunction.
(And if it is OFF in P or N position, this too is judged to
be a malfunction.) P0615
—TM-39
TRANSMISSION
CONT • TCM is malfunctioning.
P0700 P0700TM-42
T/M RANGE SWITCH A• PNP switch 1-4 signals input with impossible pattern
• “P” position is detected from N position without any
other position being detected in between. P0705 P0705
TM-43
INPUT SPEED SEN-
SOR A• TCM does not receive the proper voltage signal from
the sensor.
• TCM detects an irregularity only at position of 4th gear
for turbine revolution sensor 2. P0717 P0717
TM-46
OUTPUT SPEED SEN-
SOR• Signal from vehicle speed sensor A/T (Revolution sen-
sor) not input due to cut line or the like
• Unexpected signal input during running
• After ignition switch is turned ON, unexpected signal
input from vehicle speed sensor MTR before the vehi-
cle starts moving P0720 P0720
TM-49
ENGINE SPEED• TCM does not receive the CAN communication signal
from the ECM. P0725
—TM-51
1GR INCORRECT RA-
TIO • A/T cannot shift to 1st gear
P0731 P0731TM-54
Revision: March 2010 2008 QX56

DIAGNOSIS SYSTEM (TCM)TM-33
< FUNCTION DIAGNOSIS >
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2GR INCORRECT RA-
TIO • A/T cannot shift to 2nd gear
P0732 P0732TM-56
3GR INCORRECT RA-
TIO• A/T cannot shift to 3rd gear
P0733 P0733TM-58
4GR INCORRECT RA-
TIO• A/T cannot shift to 4th gear
P0734 P0734TM-60
5GR INCORRECT RA-
TIO• A/T cannot shift to 5th gear
P0735 P0735TM-62
TORQUE CONVERT-
ER• Normal voltage not applied to solenoid due to cut line,
short, or the like P0740 P0740
TM-63
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-66
PC SOLENOID A• 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-67
TP SENSOR• TCM does not receive the proper accelerator pedal po-
sition signals (input by CAN communication) from
ECM. P1705 P1705
TM-69
TRANS FLUID TEMP
SEN• During running, the ATF temperature sensor signal
voltage is excessively high or low P1710 P0710
TM-71
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
1ST 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-II (DTC)
Reference page
“TRANSMIS-
SION” with
CONSULT-III MIL indicator
lamp*1, “EN-
GINE” with
CONSULT-III or
GST
Revision: March 2010 2008 QX56