INFINITI QX56 2008 Factory Service Manual

EC-32
< FUNCTION DIAGNOSIS >[VK56DE]
AIR CONDITIONING CUT CONTROL
AIR CONDITIONING CUT CONTROL
Input/Output Signal ChartINFOID:0000000001351236
*1: This signal is sent to the ECM through CAN communication line.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.
System DescriptionINFOID:0000000001351237
This system improves engine operati
on when the air conditioner is used.
Under the following conditions, the air conditioner is turned OFF.
• When the accelerator pedal is fully depressed.
• When cranking the engine.
• At high engine speeds.
• When the engine coolant temperat ure becomes excessively high.
• When operating power steering during low engine speed or low vehicle speed.
• When engine speed is excessively low.
• When refrigerant pressure is excessively low or high.
Sensor Input Signal to ECMECM functionActuator
Air conditioner switch Air conditioner ON signal*
1
Air conditioner
cut controlAir conditio
ner relay
Accelerator pedal position sensor
Accelerator pedal position
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed*
2
Engine coolant temperature sensor
Engine coolant temperature
Battery Battery voltage*
2
Refrigerant pressure sensorRefrigerant pressure
Power steering pressure sensor Power steering operation
Wheel sensor Vehicle speed*
1
Revision: March 2010 2008 QX56

AUTOMATIC SPEED CONTROL DEVICE (ASCD)EC-33
< FUNCTION DIAGNOSIS > [VK56DE]
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System DescriptionINFOID:0000000001351238
INPUT/OUTPUT SIGNAL CHART
*: This signal is sent to the ECM through CAN communication line
BASIC ASCD SYSTEM
Refer to Owner's Manual for ASCD operating instructions.
Automatic Speed Control Device (ASCD) allows a driver to keep vehicle at predetermined constant speed
without depressing accelerator pedal. Driver can set
vehicle speed in advance between approximately 40 km/
h (25 MPH) and 144 km/h (89 MPH).
ECM controls throttle angle of electric thro ttle control actuator to regulate engine speed.
Operation status of ASCD is indicated by CRUISE i ndicator and SET indicator in combination meter. If any
malfunction occurs in ASCD system, it automatically deactivates control.
NOTE:
Always drive vehicle in safe manner according to traffic conditions and obey all traffic laws.
SET OPERATION
Press MAIN switch. (The CRUISE indicato r in combination meter illuminates.)
When vehicle speed reaches a desired speed between approximately 40 km/h (25 MPH) and 144 km/h (89
MPH), press SET/COAST switch. (Then SET indicator in combination meter illuminates.)
ACCELERATE OPERATION
If the RESUME/ACCELERATE switch is pressed during cr uise control driving, increase the vehicle speed until
the switch is released or vehicle speed reac hes maximum speed controlled by the system.
And then ASCD will keep the new set speed.
CANCEL OPERATION
When any of following conditions exis t, cruise operation will be canceled.
• CANCEL switch is pressed
• More than 2 switches at ASCD steer ing switch are pressed at the same time (Set speed will be cleared)
• Brake pedal is depressed
• Selector lever is changed to N, P, R position
• Vehicle speed decreased to 13 km/h (8 MPH) lower than the set speed
• VDC system is operated
When the ECM detects any of the following conditions, the ECM will cancel the cruise operation and inform
the driver by blinking indicator lamp.
• Engine coolant temperature is slightly higher than the normal operating temperature, CRUISE lamp may
blink slowly.
When the engine coolant temperature decreases to t he normal operating temperature, CRUISE lamp will
stop blinking and the cruise operation will be able to work by pressing SET/COAST switch or RESUME/
ACCELERATE switch.
• Malfunction for some self-diagnoses regarding ASCD control: SET lamp will blink quickly.
If MAIN switch is turned to OFF during ASCD is activated, all of ASCD operations will be canceled and vehicle
speed memory will be erased.
COAST OPERATION
When the SET/COAST switch is pressed during cruise control driving, decrease vehicle set speed until the
switch is released. And then ASCD will keep the new set speed.
RESUME OPERATION
Sensor Input signal to ECM ECM functionActuator
ASCD brake switch Brake pedal operation
ASCD vehicle speed controlElectric throttle control
actuator
Stop lamp switch
Brake pedal operation
ASCD steering switch ASCD steering switch operation
Wheel sensor Vehicle speed*
TCM Powertrain revolution*
Gear position
Revision: March 2010
2008 QX56

EC-34
< FUNCTION DIAGNOSIS >[VK56DE]
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
When the RESUME/ACCELERATE
switch is pressed after cancel operation other than pressing MAIN switch
is performed, vehicle speed will return to last set s peed. To resume vehicle set speed, vehicle condition must
meet following conditions.
• Brake pedal is released
• A/T selector lever is in other than P and N positions
• Vehicle speed is greater than 40 km/h (25 MPH) and less than 144 km/h (89 MPH)
Component DescriptionINFOID:0000000001351239
ASCD STEERING SWITCH
Refer to EC-336.
ASCD BRAKE SWITCH
Refer to EC-347, and EC-390.
STOP LAMP SWITCH
Refer to EC-347, EC-356 and EC-390.
ELECTRIC THROTTLE CONTROL ACTUATOR
Refer to EC-359, EC-362, EC-366 and EC-368.
ASCD INDICATOR
Refer to EC-394.
Revision: March 2010 2008 QX56

CAN COMMUNICATIONEC-35
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CAN COMMUNICATION
System DescriptionINFOID:0000000001351240
CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle mul-
tiplex communication line with high data communication speed and excellent error detection ability. Many elec-
tronic control units are equipped onto a vehicle, and each
control unit shares information and links with other
control units during operation (not independent). In CAN communication, control units are connected with 2
communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only.
Refer to LAN-44, "
CAN System Specification Chart", about CAN communication for detail.
Revision: March 2010 2008 QX56

EC-36
< FUNCTION DIAGNOSIS >[VK56DE]
COOLING FAN CONTROL
COOLING FAN CONTROL
DescriptionINFOID:0000000001351873
SYSTEM DESCRIPTION
Cooling Fan Control
*1: The ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to ECM through CAN communication line.
The ECM controls the cooling fan corresponding to the
vehicle speed, engine coolant temperature, refrigerant
pressure, and air conditioner ON signal. The c ontrol system has 2-step control [HI/OFF].
Cooling Fan Operation
SensorInput signal to ECMECM functionActuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed*
1
Cooling fan
controlIPDM E/R
(Cooling fan relay)
Battery
Battery voltage*
1
Wheel sensorVehicle speed*2
Engine coolant temperature sensor Engine coolant temperature
Air conditioner switch Air conditioner ON signal*
2
Refrigerant pressure sensorRefrigerant pressure
PBIB2060E
Revision: March 2010 2008 QX56

EVAPORATIVE EMISSION SYSTEMEC-37
< FUNCTION DIAGNOSIS > [VK56DE]
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EVAPORATIVE EMISSION SYSTEM
DescriptionINFOID:0000000001351241
SYSTEM DESCRIPTION
The evaporative emission system is used to reduce hydr
ocarbons emitted into the atmosphere from the fuel
system. This reduction of hydrocarbons is accompli shed by activated charcoals in the EVAP canister.
The fuel vapor in the sealed fuel tank is led into the EVAP canister which contains activated carbon and the
vapor is stored there when the engine is not oper ating or when refueling to the fuel tank.
The vapor in the EVAP canister is purged by the air through the purge line to the intake manifold when the
engine is operating. EVAP canister purge volume control solenoid valve is controlled by ECM. When the
engine operates, the flow rate of vapor controlled by EVAP canister purge volume control solenoid valve is
proportionally regulated as the air flow increases.
EVAP canister purge volume control solenoid valve al so shuts off the vapor purge line during decelerating and
idling.
PBIB1631E
Revision: March 2010 2008 QX56

EC-38
< FUNCTION DIAGNOSIS >[VK56DE]
EVAPORATIVE EMISSION SYSTEM
EVAPORATIVE EMISSION LINE DRAWING
PBIB2053E
Revision: March 2010
2008 QX56

EVAPORATIVE EMISSION SYSTEMEC-39
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BBIA0444E
Revision: March 2010
2008 QX56

EC-40
< FUNCTION DIAGNOSIS >[VK56DE]
INTAKE VALVE TIMING CONTROL
INTAKE VALVE TIMING CONTROL
DescriptionINFOID:0000000001351376
SYSTEM DESCRIPTION
*: This signal is sent to the ECM through CAN communication line
This mechanism hydraulically controls cam phases c
ontinuously with the fixed operating angle of the intake
valve.
The ECM receives signals such as crankshaft posit ion, camshaft position, engine speed, and engine coolant
temperature. Then, the ECM sends ON/OFF pulse duty si gnals to the intake valve timing (IVT) control sole-
noid valve depending on driving status. This makes it po ssible to control the shut/open timing of the intake
valve to increase engine torque in low/mid speed range and output in high-speed range.
Sensor Input signal to ECM function ECMActuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed
Intake valve
timing controlIntake valve timing control
solenoid valve
Intake valve timing control position sensor Intake valve timing signal
Engine coolant temperature sensor
Engine coolant temperature
Wheel sensor Vehicle speed*
PBIB3276E
Revision: March 2010 2008 QX56

ON BOARD DIAGNOSTIC (OBD) SYSTEMEC-41
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ON BOARD DIAGNOSTIC (OBD) SYSTEM
IntroductionINFOID:0000000001351323
The ECM has an on board diagnostic system, which detects malfunctions related to engine sensors or actua-
tors. The ECM also records various emission-related diagnostic information including:
The above information can be checked using procedures listed in the table below.
×
: Applicable —: Not applicable
*: When DTC and 1st trip DTC simultaneously appear on the display, they cannot be clearly distinguished from each other.
The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected
in two consecutive trips (Two trip detection logic) , or when the ECM enters fail-safe mode. (Refer to EC-459,
"Fail-Safe Chart".)
Two Trip Detection LogicINFOID:0000000001351324
When a malfunction is detected for the first time, 1st tr ip DTC and 1st trip Freeze Frame data are stored in the
ECM memory. The MIL will not light up at this stage. <1st trip>
If the same malfunction is detected again during the next drive, the DTC and Freeze Frame data are stored in
the ECM memory, and the MIL lights up. The MIL lights up at the same time when the DTC is stored. <2nd
trip> The “trip” in the “Two Trip Detection Logic” m eans a driving mode in which self-diagnosis is performed
during vehicle operation. Specific on board diagnostic item s will cause the ECM to light up or blink the MIL,
and store DTC and Freeze Frame data, even in the 1st trip, as shown below.
× : Applicable —: Not applicable
When there is an open circuit on MIL circuit, the ECM c annot warn the driver by lighting up MIL when there is
malfunction on engine control system.
Emission-related diagnostic information Diagnostic service
Diagnostic Trouble Code (DTC) Service $03 of SAE J1979
Freeze Frame data Service $02 of SAE J1979
System Readiness Test (SRT) code Service $01 of SAE J1979
1st Trip Diagnostic Trou ble Code (1st Trip DTC) Service $07 of SAE J1979
1st Trip Freeze Frame data
Test values and Test limits Service $06 of SAE J1979
Calibration ID Service $09 of SAE J1979
DTC 1st trip DTC Freeze
Frame data 1st trip Freeze
Frame data SRT code SRT status Test value
CONSULT-III ×× × × × × —
GST ×× × —×××
ECM ××*— — — ×—
Items MIL
DTC1st trip DTC
1st trip 2nd trip
1st trip
displaying 2nd trip
displaying 1st trip
displaying 2nd trip
display- ing
Blinking Lighting
up Blinking Lighting
up
Misfire (Possible three way catalyst
damage) — DTC: P0300 - P0308 is
being detected ×
———— — ×—
Misfire (Possible three way catalyst
damage) — DTC: P0300 - P0308 is
being detected ——
×—— ×——
One trip detection diagnoses (Re-
fer to EC-462, "
DTC Index".) —
×—— ×———
Except above — — —×— ×× —
Revision: March 2010 2008 QX56