INFINITI QX56 2010 Factory Service Manual

EC-28
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MULTIPORT FUEL INJECTION SYSTEM
MULTIPORT FUEL INJECTION SYSTEM
System DescriptionINFOID:0000000005149064
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system. This is used only for the on board diagnosis.
*2: This signal is sent to the ECM through CAN communication line.
*3: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION
The amount of fuel injected from the fuel injector is
determined by the ECM. The ECM controls the length of
time the valve remains open (injection pulse duration). T he amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air
flow sensor.
VARIOUS FUEL INJECTION I NCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated to improve engine performance under various operat-
ing conditions as listed below.
• During warm-up
• When starting the engine
• During acceleration
• Hot-engine operation
• When selector lever is changed from N to D
• High-load, high-speed operation

• During deceleration
• During high engine speed operation
Sensor Input signal to ECMECM functionActuator
Crankshaft position sensor (POS) Engine speed*
3
Piston position
Fuel injection
& mixture ratio
controlFuel injector
Camshaft position sensor (PHASE)
Mass air flow sensor
Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
TCM Gear position
Knock sensor Engine knocking condition
Battery Battery voltage*
3
Power steering pressure sensorPower steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
ABS actuator and electric unit (control unit) VDC/TCS operation command*
2
Air conditioner switchAir conditioner operation*2
Wheel sensorVehicle speed*2
Revision: April 20092010 QX56

MULTIPORT FUEL INJECTION SYSTEMEC-29
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MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system prov
ides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst (manifold) can then better r educe CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The
ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to EC-137
. This maintains the mixture ratio within the range of stoichiometric
(ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the th ree way catalyst (manifold). Even if the switching
characteristics of air fuel ratio (A/F) sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Open Loop Control
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
• Deceleration and acceleration
• High-load, high-speed operation
• Malfunction of A/F sensor 1 or its circuit
• Insufficient activation of A/F sensor 1 at low engine coolant temperature
• High engine coolant temperature
• During warm-up
• After shifting from N to D
• When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from A/F sensor 1.
This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoret-
ical mixture ratio as possible. However, the basic mi xture ratio is not necessarily controlled as originally
designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes dur-
ing operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is
then computed in terms of “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value co mpared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensati on used to maintain the mixture ratio at its theoretical
value. The signal from A/F sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the the-
oretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in
fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation ca rried out long-term to compensate for continual deviation
of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
PBIB3020E
Revision: April 20092010 QX56

EC-30
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MULTIPORT FUEL INJECTION SYSTEM
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport
Fuel Injection System
Fuel is injected simultaneously into all eight cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The eight fuel injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.
FUEL SHUT-OFF
Fuel to each cylinder is cut off during deceleration, operation of the engine at excessively high speeds or oper-
ation of the vehicle at excessively high speed.
PBIB0122E
Revision: April 20092010 QX56

ELECTRIC IGNITION SYSTEMEC-31
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ELECTRIC IGNITION SYSTEM
System DescriptionINFOID:0000000005149065
INPUT/OUTPUT SIGNAL CHART
*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 DESCRIPTION
Firing order: 1 - 8 - 7 - 3 - 6 - 5 - 4 -2
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of the
engine. The ignition timing data is stored in the ECM.
The ECM receives information such as the injection
pulse width and camshaft position sensor signal. Comput-
ing this information, ignition signals are transmitted to the power transistor.
During the following conditions, the ignition timing is revi sed by the ECM according to the other data stored in
the ECM.
• At starting
• During warm-up
•At idle
• At low battery voltage
• During acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.
SensorInput signal to ECMECM functionActuator
Crankshaft position sensor (POS) Engine speed*
2
Piston position
Ignition timing
controlPower transistor
Camshaft position sensor (PHASE)
Mass air flow sensor
Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Knock sensor Engine knocking
TCM Gear position
Battery Battery voltage*
2
Wheel sensor
Vehicle speed*1
Revision: April 20092010 QX56

EC-32
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AIR CONDITIONING CUT CONTROL
AIR CONDITIONING CUT CONTROL
Input/Output Signal ChartINFOID:0000000005149066
*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:0000000005149067
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: April 20092010 QX56

AUTOMATIC SPEED CONTROL DEVICE (ASCD)EC-33
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System DescriptionINFOID:0000000005149068
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 indicator may
blink slowly.
When the engine coolant temperature decreases to the normal operating temperature, CRUISE indicator 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 indicator 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 Gear position
Powertrain revolution*
Revision: April 20092010 QX56

EC-34
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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:0000000005149069
ASCD STEERING SWITCH
Refer to EC-332.
ASCD BRAKE SWITCH
Refer to EC-344, and EC-388.
STOP LAMP SWITCH
Refer to EC-344, EC-353 and EC-388.
ELECTRIC THROTTLE CONTROL ACTUATOR
Refer to EC-356, EC-359, EC-363 and EC-365.
ASCD INDICATOR
Refer to EC-391.
Revision: April 20092010 QX56

CAN COMMUNICATIONEC-35
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CAN COMMUNICATION
System DescriptionINFOID:0000000005149070
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: April 20092010 QX56

EC-36
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COOLING FAN CONTROL
COOLING FAN CONTROL
DescriptionINFOID:0000000005149071
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: April 20092010 QX56

EVAPORATIVE EMISSION SYSTEMEC-37
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EVAPORATIVE EMISSION SYSTEM
DescriptionINFOID:0000000005149072
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: April 20092010 QX56