2010 INFINITI QX56 Factory Service Manual

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Page 1377 of 4210

INFINITI QX56 2010 Factory Service Manual EC-24
< FUNCTION DIAGNOSIS >[VK56DE]
ENGINE CONTROL SYSTEM
10. Camshaft position sensor (PHASE) 11
. Electric throttle control actuator
(view with intake air duct removed) 12. Cooling fan motor harn

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INFINITI QX56 2010 Factory Service Manual ENGINE CONTROL SYSTEMEC-25
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1. EVAP canister purge volume control
solenoid valve (view with engine
cover removed) 2. EVAP service port

Page 1379 of 4210

INFINITI QX56 2010 Factory Service Manual EC-26
< FUNCTION DIAGNOSIS >[VK56DE]
ENGINE CONTROL SYSTEM
1. Knock sensor (bank 1) (view with en-
gine removed) 2. Knock sensor (bank 2) (view with en-
gine removed) 3. Battery current sensor
4. Powe

Page 1380 of 4210

INFINITI QX56 2010 Factory Service Manual ENGINE CONTROL SYSTEMEC-27
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PBIB2639E
Revision: April 20092010 QX56

Page 1381 of 4210

INFINITI QX56 2010 Factory Service Manual EC-28
< FUNCTION DIAGNOSIS >[VK56DE]
MULTIPORT FUEL INJECTION SYSTEM
MULTIPORT FUEL INJECTION SYSTEM
System DescriptionINFOID:0000000005149064
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to

EC-28
< FUNCTION DIAGNOSIS >[VK56DE]
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

Page 1382 of 4210

INFINITI QX56 2010 Factory Service Manual MULTIPORT FUEL INJECTION SYSTEMEC-29
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MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system prov
ides th

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

Page 1383 of 4210

INFINITI QX56 2010 Factory Service Manual EC-30
< FUNCTION DIAGNOSIS >[VK56DE]
MULTIPORT FUEL INJECTION SYSTEM
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder

Page 1384 of 4210

INFINITI QX56 2010 Factory Service Manual ELECTRIC IGNITION SYSTEMEC-31
< FUNCTION DIAGNOSIS > [VK56DE]
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ELECTRIC IGNITION SYSTEM
System DescriptionINFOID:0000000005149065
INPUT/OUTPUT SIGNAL CHART
*1: This sign

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