2011 INFINITI QX56 air condition

STRUCTURE AND OPERATIONEC-33
< SYSTEM DESCRIPTION > [VK56VD]
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STRUCTURE AND OPERATION
Positive Crankcase VentilationINFOID:0000000006217695
This system returns blow-by gas to the intake manifold.
The positive crankcase ventilation (PCV) valve is prov
ided to conduct crankcase blow-by gas to the intake
manifold.
During partial throttle operation of the engine, the in take manifold sucks the blow-by gas through the PCV
valve.
Normally, the capacity of the valve is sufficient to handle any blow-by and a small amount of ventilating air.
The ventilating air is drawn from the air inlet tubes in to the crankcase. In this process the air passes through
the hose connecting air inlet tubes to rocker cover.
Under full-throttle condition, the manifold vacuum is in sufficient to draw the blow-by flow through the valve.
The flow goes through the hose connection in the reverse direction.
On vehicles with an excessively high blow-by, the valve does not
meet the requirement. This is because some of the flow will go
through the hose connection to the air inlet tubes under all condi-
tions.
PBIB0062E
PBIB1588E
Revision: 2010 May2011 QX56

EC-36
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
DIRECT INJECTION GASOLINE SYSTEM
DIRECT INJECTION GASOLINE
SYSTEM : System DiagramINFOID:0000000006217699
DIRECT INJECTION GASOLINE SY STEM : System DescriptionINFOID:0000000006217700
INPUT/OUTPUT SIGNAL CHART
Function Reference
Fuel injection control EC-36, "
DIRECT INJECTION GASOLINE
SYSTEM : System De-
scription"
Fuel pressure control EC-39, "FUEL PRESSURE CONTROL : System Description"
Cooling fan controlEC-41, "COOLING FAN CONTROL : System Description"
Electric ignition controlEC-42, "ELECTRIC IGNITION SYSTEM : System Description"
Intake valve timing controlEC-43, "INTAKE VALVE TIMING CONTROL : System Description"
VVEL (Variable Valve Event & Lift) EC-44, "VVEL SYSTEM : System Description"
Evaporative emissionEC-45, "EVAPORATIVE EMISSION SYSTEM : System Descrip-
tion"
Air conditioning cut controlEC-47, "AIR CONDITIONING CUT CONT
ROL : System Descrip-
tion"
ASCD (Auto speed control device) EC-48, "AUTOMATIC SPEED CONTROL DEVICE (ASCD) : Sys-
tem Description"
Power generation voltage variable controlCHG-7, "POWER GENERATION VOLTAGE VARIABLE CON-
TROL SYSTEM : System Description"
JSBIA0471GB
Revision: 2010 May2011 QX56

SYSTEMEC-37
< SYSTEM DESCRIPTION > [VK56VD]
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*1: This sensor is not used to control the engine system under normal conditions.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION
The adoption of the direct fuel injection method enables
more accurate adjustment of fuel injection quantity by
injecting atomized high-pressure fuel directly into the cylinder. This method allows high-powered engine, low
fuel consumption, and emissions-reduction.
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 engi ne operating conditions. These conditions are determined
by input signals (for engine speed and intake air and fuel rail pressure) from the crankshaft position sensor,
camshaft position sensor, mass air flow sensor and the fuel rail pressure sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compens ated 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 position is changed from N to D
 High-load, high-speed operation

 During deceleration
 During high engine speed operation
FUEL INJECTION CONTROL
Stratified-charge Combustion
Stratified-charge combustion is a combustion method wh ich enables extremely lean combustion by injecting
fuel in the latter half of a compression process, coll ecting combustible air-fuel around the spark plug, and form-
ing fuel-free airspace around the mixture.
Right after a start with the engine cold, the catalyst warm-up is accelerated by stratified-charge combustion.
Homogeneous Combustion
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor Engine speed*
2
Fuel injection
& mixture ratio
controlFuel injector
Camshaft position sensor Camshaft position
Mass air flow sensor Amount of intake air
Intake air temperature sensor Intake air temperature
Engine coolant temperature sensor Engine coolant temperature
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
Fuel rail pressure sensor Fuel rail pressure
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
TCM Gear position
Battery
Battery voltage*
2
Knock sensor Engine knocking condition
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
ABS actuator and electric unit (control unit) VDC/TCS operation command
A/C auto amp. A/C ON signal
Combination meter Vehicle speed
Revision: 2010 May2011 QX56

EC-38
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
Homogeneous combustion is a combustion method that fuel
is injected during intake process so that combus-
tion occurs in the entire combustion chamber , as is common with conventional methods.
As for a start except for starts with the engine cold, homogeneous combustion occurs.
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 better reduce CO , HC and NOx emissions. This system uses A/F sen-
sor 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 A/F sensor 1, refer to
EC-21, "
Air Fuel Ratio (A/F) Sensor 1". 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 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 t he mixture ratio signal transmitted from A/F sensor 1.
This feedback signal is then sent to the ECM. The ECM c ontrols 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 ai r flow sensor hot wire) and characteristic changes dur-
ing operation (i.e., fuel 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 carri ed out over time to compensate for continual deviation
of the “short-term fuel trim” from the central value. Continual deviation will occur due to individual engine differ-
ences, wear over time and changes in the usage environment.
FUEL INJECTION TIMING
Sequential Direct Injection Gasoline System
PBIB2793E
Revision: 2010 May2011 QX56

SYSTEMEC-41
< SYSTEM DESCRIPTION > [VK56VD]
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COOLING FAN CONTROL : System DiagramINFOID:0000000006217703
COOLING FAN CONTROL : System DescriptionINFOID:0000000006217704
INPUT/OUTPUT SIGNAL CHART
*1: The ECM determines the engine speed by the signals of crankshaft position and camshaft position.
*2: This signal is sent to ECM via the CAN communication line.
SYSTEM DESCRIPTION
 Based on a signal transmitted from each sensor, ECM calc
ulates a target fan speed responsive to a driving
condition. In addition, ECM calculates a fan pulley speed according to an engine speed and transmits a cool-
ing fan request signal to IPDM E/R via the CAN comm unication line to satisfy the target fan speed. Then,
IPDM E/R transmits ON/OFF pulse duty signal to electrically-controlled cooling fan coupling.
The cooling fan speed sensor detects a cooling f an speed and transmits the detection result to ECM.
 ECM judges the start signal state from the engine speed signal and battery voltage.
ELECTRIC IGNITION SYSTEM
JSBIA0237GB
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor Engine speed*
1
Cooling fan speed request
signal*2
IPDM E/R
↓
Electrically-controlled cooling fan
coupling
Camshaft position sensor Camshaft position
Engine coolant temperature sensor Engine coolant temperature
Refrigerant pressure sensor Refrigerant pressure
Intake air temperature sensor Intake air temperature
Battery Battery voltage
Combination meter
Vehicle speed signal*
2
BCMA/C switch signal*2
Cooling fan speed sensor Cooling fan speed
Revision: 2010 May2011 QX56

EC-42
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
ELECTRIC IGNITION SYSTEM : System Diagram
INFOID:0000000006217705
ELECTRIC IGNITION SYSTEM : System DescriptionINFOID:0000000006217706
INPUT/OUTPUT SIGNAL CHART
*1: ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to the ECM via the CAN communication line.
SYSTEM DESCRIPTION
Ignition 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 re vised 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.
JPBIA3271GB
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor Engine speed*
1
Piston position
Ignition timing
controlIgnition coil
(with power transistor)
Camshaft position sensor
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
TCM Gear position
Battery
Battery voltage*
1
Knock sensor Engine knocking condition
Combination meterVehicle speed*
2
Revision: 2010 May2011 QX56

EC-46
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
*1: ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to the ECM via the CAN communication line.
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 accomplis hed by activated charcoals in the EVAP canister.
The fuel vapor in the sealed fuel tank is led into t he 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 contro l 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 also shuts off the vapor purge line during decelerating and
idling.
AIR CONDITIONING CUT CONTROL
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor
Camshaft position sensor  Engine speed*
1
 Piston position
EVAP canister
purge flow controlEVAP canister purge volume
control solenoid valve
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Battery
Battery voltage*
1
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
(Mixture ratio
feedback signal)
Fuel tank temperature sensor Fuel temperature in fuel tank
EVAP control system pressure sensor Pressure in purge line
Combination meter Vehicle speed*
2
PBIB1631E
Revision: 2010 May2011 QX56

SYSTEMEC-47
< SYSTEM DESCRIPTION > [VK56VD]
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AIR CONDITIONING CUT CONTROL : System DiagramINFOID:0000000006217713
AIR CONDITIONING CUT CONTROL : System DescriptionINFOID:0000000006217714
INPUT/OUTPUT SIGNAL CHART
*1: This signal is sent to the ECM via the CAN communication line.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION
This system improves engine operation 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 temperature 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.
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
JMBIA1457GB
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor
Camshaft position sensor Engine speed*
2
Air conditioner cut
controlIPDM E/R
↓
A/C relay
↓
Compressor
Engine coolant temperature sensor Engine coolant temperature
Accelerator pedal position sensor Accelerator pedal position
Battery
Battery voltage*
2
Refrigerant pressure sensor Refrigerant pressure
Power steering pressure sensor Power steering operation
A/C auto amp.A/C ON signal*
1
A/C evaporator temperature*1
Target A/C evaporator temperature*1
Blower fan ON signal
Combination meter Vehicle speed*
1
Revision: 2010 May2011 QX56