2011 INFINITI QX56 ESP

COMPONENT PARTSEC-21
< SYSTEM DESCRIPTION > [VK56VD]
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Accelerator Pedal
Position SensorINFOID:0000000006217658
The accelerator pedal position (APP) sensor is installed on the
accelerator pedal assembly. The sensor detects the accelerator
position and sends a signal to the ECM.
Accelerator pedal position sensor has two sensors. These sensors
are a kind of potentiometer which transform the accelerator pedal
position into output voltage, and emit the voltage signals to the ECM.
The ECM judges the current opening angle of the accelerator pedal
from these signals and controls the throttle control motor based on
these signals.
Idle position of the accelerator pedal is determined by the ECM
receiving the signal from the accelerator pedal position sensor. The
ECM uses this signal for engine operations such as fuel cut.
Air Fuel Ratio (A/F) Sensor 1INFOID:0000000006217659
DESCRIPTION
The sensor element of the A/F sensor 1 is composed an electrode layer, which transports ions. It has a heater
in the element.
The sensor is capable of precise measurement = 1, but also in the lean and rich range. Together with its
control electronics, the sens or outputs a clear, continuous signal throughout a wide range.
The exhaust gas components diffuse through the diffusion layer at the sensor cell. An electrode layer is
applied voltage, and this current relative oxygen density in lean. Also this current relative hydrocarbon density
in rich.
Therefore, the A/F sensor 1 is able to indicate air fuel ratio by this
electrode layer of current. In addition, a heater is integrated in the
sensor to ensure the required operating temperature of approxi-
mately 760 °C (1,400 °F).
A/F SENSOR 1 HEATER
A/F sensor 1 heater is integrated in the sensor.
The ECM performs ON/OFF duty control of the A/F sensor 1 heater corresponding to the engine operating
condition to keep the temperature of A/F s ensor 1 element within the specified range.
ASCD Brake Switch & Stop Lamp Switch INFOID:0000000006217660
Stop lamp switch and ASCD brake switch are installed to brake pedal bracket.
When the brake pedal is depressed, ASCD brake switch is turned OFF and stop lamp switch is turned ON.
ECM detects the state of the brake pedal by those two types of input (ON/OFF signal).
ASCD Steering SwitchINFOID:0000000006217661
ASCD steering switch has variant values of electrical resistance for each button. ECM reads voltage variation
of switch, and determines which button is operated.
ASCD IndicatorsINFOID:0000000006217662
ASCD operation status is indicated by CRUISE indicator in combination meter.
ECM transmits the ASCD status signal to the combi nation meter via CAN communication according to ASCD
operation.
PBIB1741E
JSBIA0527GB
Revision: 2010 May2011 QX56

EC-24
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
Electric throttle control actuator consists of throttle bod
y, throttle valve, throttle control motor and throttle posi-
tion sensor.
THROTTLE CONTROL MOTOR
The throttle control motor is operated by the ECM and it opens and closes the throttle valve.
The current opening angle of the throttle valve is detected by the throttle position sensor. The throttle position
sensor provides feedback to the ECM, when opens/closes the throttle valve in response to driving conditions
via the throttle control motor.
THROTTLE POSITION SENSOR
The throttle position (TP) sensor responds to the throttle valve move-
ment.
The throttle position sensor has two sensors. These sensors are a
kind of potentiometer which transform the throttle valve position into
output voltage, and emit the voltage signal to the ECM. The ECM
judges the current opening angle of the throttle valve from these sig-
nals and controls the throttle valve opening angle in response to
driving conditions via the throttle control motor.
Electrically-controlled cooling fan couplingINFOID:0000000006217668
Electrically-controlled cooling fan coupling is integrat ed with a fan coupling, fan coupling driver, and fan speed
sensor, mounted to the fan pulley, and actuated by the dr ive belt to rotate the cooling fan at a speed suitable
for a driving condition.
JSBIA0270GB
PBIB0145E
JSBIA0289ZZ
Revision: 2010 May2011 QX56

EC-26
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
EVAP Control System Pressure Sensor
INFOID:0000000006256476
The EVAP control system pressure s ensor detects pressure in the
purge line. The sensor output voltage to the ECM increases as pres-
sure increases.
EVAP Canister Vent Control ValveINFOID:0000000006256477
The EVAP canister vent control valve is located on the EVAP canis-
ter and is used to seal the canister vent.
This solenoid valve responds to signals from the ECM. When the
ECM sends an ON signal, the coil in the solenoid valve is energized.
A plunger will then move to seal the canister vent. The ability to seal
the vent is necessary for the on board diagnosis of other evaporative
emission control system components.
This solenoid valve is used only for diagnosis, and usually remains
opened.
When the vent is closed, under normal purge conditions, the evapo-
rative emission control system is depressurized and allows “EVAP
Control System” diagnosis.
EVAP Canister Purge Volume Control Solenoid ValveINFOID:0000000006217671
The EVAP canister purge volume control solenoid valve is used to
control the flow rate of fuel vapor from the EVAP canister. The EVAP
canister purge volume control solenoid valve is moved by ON/OFF
pulses from the ECM. The longer the ON pulse, the greater the
amount of fuel vapor that will flow through the valve.
Fuel InjectorINFOID:0000000006217672
For the fuel injector, a high pressure fuel injector is used and this
enables a high-pressure fuel injection at a high voltage within a short
time. The ECM is equipped with an injector driver unit and actuates
the fuel injector at a high volt age (approximately 65 V at the maxi-
mum).
Fuel Level SensorINFOID:0000000006217673
The fuel level sensor is mounted in the fuel level sensor unit.
PBIB3370E
PBIB1263E
JMBIA0069ZZ
JSBIA0287ZZ
Revision: 2010 May2011 QX56

EC-28
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
The heated oxygen sensor 2, after three way catalyst (manifold),
monitors the oxygen level in the exhaust gas on each bank.
Even if switching characteristics of
the air fuel ratio (A/F) sensor 1
are shifted, the air fuel ratio is c ontrolled to stoichiometric, by the sig-
nal from the heated oxygen sensor 2.
This sensor is made of ceramic zirconia. The zirconia generates volt-
age from approximately 1 V in richer conditions to 0 V in leaner con-
ditions.
Under normal conditions the heated ox ygen sensor 2 is not used for
engine control operation.
HEATED OXYGEN SENSOR 2 HEATER
Heated oxygen sensor 2 heater is integrated in the sensor.
The ECM performs ON/OFF control of the heated oxy gen sensor 2 heater corresponding to the engine speed,
amount of intake air and engine coolant temperature.
High Pressure Fuel PumpINFOID:0000000006217678
The high pressure fuel pump is installed at the front of the engine bank 2 side and activated by the camshaft.
ECM controls the high pressure fuel pump control sol enoid valve built into the high pressure fuel pump and
adjusts the amount of discharge by changing the suction timing of the low pressure fuel.
Operating Description
SEF327R
Engine speed Heated oxygen sensor 2 heater
Above 3,600 rpm OFF
Below 3,600 rpm after the following conditions are met.
 Engine: After warming up
 Keeping the engine speed between 3,500 and 4,000 rpm for 1 minute and at idle for 1 minute under no load ON
JSBIA0285GB
Revision: 2010 May2011 QX56

COMPONENT PARTSEC-31
< SYSTEM DESCRIPTION > [VK56VD]
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Manifold Absolute Pressure SensorINFOID:0000000006217687
The manifold absolute pressure (MAP) sensor is installed on the
intake manifold collector. Detects intake manifold pressure, and
transmits a voltage signal to the ECM.
The sensor uses a silicon diaphragm which is sensitive to the
change in pressure. As the pressu
re increases, the voltage rises.
Mass Air Flow Sensor (With Intake Air Temperature Sensor)INFOID:0000000006217688
MASS AIR FLOW SENSOR
The mass air flow (MAF) sensor (1) is placed in the stream of intake
air. It measures the intake flow ra te by measuring a part of the entire
intake flow. The mass air flow sens or controls the temperature of the
hot wire to a certain amount. The heat generated by the hot wire is
reduced as the intake air flows around it. The greater air flow, the
greater the heat loss.
Therefore, the electric current supplied to hot wire is changed to
maintain the temperature of the hot wire as air flow increases. The
ECM detects the air flow by means of this current change.
INTAKE AIR TEMPERATURE SENSOR
The intake air temperature (IAT) sensor is built-into t he mass air flow sensor. The sensor detects intake air
temperature and transmits a signal to the ECM.
The temperature sensing unit uses a thermistor which is sensitive to the change in temperature. Electrical
resistance of the thermistor decreases in response to the rise in temperature.

*: These data are reference values and are measured between ECM terminals.
Power Steering Pressure (PSP) SensorINFOID:0000000006217689
Power steering pressure (PSP) sensor is installed to the power steering high-pressure tube and detects a
power steering load.
This sensor is a potentiometer which transforms the power steering load into output voltage, and emits the
voltage signal to the ECM. The ECM controls the electric throttle control actuator and adjusts the throttle valve
opening angle to increase the engine speed and adjusts the idle speed for the increased load.
JMBIA0877ZZ
PBIA9559J
Intake air temperature
[° C ( °F)] Voltage* (V) Resistance (k
Ω)
25 (77) 3.3 1.94 - 2.06
80 (176) 1.2 0.293 - 0.349
SEF012P
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

SYSTEMEC-45
< SYSTEM DESCRIPTION > [VK56VD]
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VVEL (Variable Valve Event & Lift) is a system that
controls valve event and valve lift continuously.
ECM decides the target valve lift according to the driving condition and sends the command signal to the
VVEL control module via ENG communication line.
VA LV E L I F T O P E R AT I O N
Rotational movement of the drive shaft equipped with eccentric cam
is transmitted to output cam via the rocker arm and two kinds of links
to depress the intake valve.
VA R I A B L E O P E R AT I O N
VVEL control module controls the ro tation of the control shaft using
the VVEL actuator motor assembly and changes the movement of
the output cam by shifting the link supporting point. As a result, valve
lift changes continuously to improve engine output and response.
EVAPORATIVE EMISSION SYSTEM
EVAPORATIVE EMISSION SYSTEM : System DiagramINFOID:0000000006256911
EVAPORATIVE EMISSION SYSTEM : System DescriptionINFOID:0000000006256912
INPUT/OUTPUT SIGNAL CHART
1. Link B
2. Output cam
3. Eccentric cam
4. Drive shaft
5. Link A
6. Rocker arm
JSBIA0464ZZ
1. Link B
2. Output cam
3. Control shaft
4. Rocker arm
JSBIA0465ZZ
JSBIA0371GB
Revision: 2010 May2011 QX56

DIAGNOSIS SYSTEM (ECM)EC-59
< SYSTEM DESCRIPTION > [VK56VD]
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The SRT will also indicate “INCMP” if the self-diagnosis
memory is erased for any reason or if the ECM mem-
ory power supply is interrupted for several hours.
If, during the state emissions inspection, the SRT indica tes “CMPLT” for all test items, the inspector will con-
tinue with the emissions test. However, if the SRT i ndicates “INCMP” for one or more of the SRT items the
vehicle is returned to the customer untested.
NOTE:
If MIL is ON during the state emissi ons inspection, the vehicle is also returned to the customer untested even
though the SRT indicates “CMPLT” for all test items. T herefore, it is important to check SRT (“CMPLT”) and
DTC (No DTCs) before the inspection.
SRT SET TIMING
SRT is set as “CMPLT” after self-diagnosis has been performed one or more times. Completion of SRT is
done regardless of whether the result is OK or NG. T he set timing is different between OK and NG results and
is shown in the table below.
OK: Self-diagnosis is carried out and the result is OK.
NG: Self-diagnosis is carried out and the result is NG.
—: Self-diagnosis is not carried out.
When all SRT related self-diagnoses show OK results in a single cycle (Ignition OFF-ON-OFF), the SRT will
indicate “CMPLT”. → Case 1 above
When all SRT related self-diagnoses show OK results through several different cycles, the SRT will indicate
“CMPLT” at the time the respective se lf-diagnoses have at least one OK result. → Case 2 above
If one or more SRT related self-diagnoses show NG results in 2 consecutive cycles, the SRT will also indicate
“CMPLT”. → Case 3 above
The table above shows that the minimum number of cycles for setting SRT as “INCMP” is the number one (1)
for each self-diagnosis (Case 1 & 2) or the number two (2) for one of self-diagnoses (Case 3). However, in
preparation for the state emissions inspection, it is unnecessary for each self-diagnosis to be executed twice
(Case 3) for the following reasons:
 The SRT will indicate “CMPLT” at the time the respective self-diagnoses have one (1) OK result.
 The emissions inspection requires “CMPLT” of the SRT only with OK self-diagnosis results.
 During SRT driving pattern, the 1st trip DTC (NG) is detected prior to “CMPLT” of SRT and the self-diagnosis
memory must be erased from the ECM after repair.
 If the 1st trip DTC is erased, all the SRT will indicate “INCMP”.
NOTE:
SRT can be set as “CMPLT” together with the DTC(s) . Therefore, DTC check must always be carried out
prior to the state emission inspection even though the SRT indicates “CMPLT”.
Self-diagnosis result Example
Diagnosis Ignition cycle
← ON →OFF ← ON →OFF ← ON →OFF ← ON →
All OK Case 1 P0400 OK (1) — (1) OK (2) — (2) P0402 OK (1) — (1) — (1) OK (2)
P1402 OK (1) OK (2) — (2) — (2)
SRT of EGR “CMPLT” “CMPLT” “CMPLT” “CMPLT”
Case 2 P0400 OK (1) — (1) — (1) — (1) P0402 — (0) — (0) OK (1) — (1)
P1402 OK (1) OK (2) — (2) — (2)
SRT of EGR “INCMP” “INCMP” “CMPLT” “CMPLT”
NG exists Case 3 P0400 OK OK — — P0402 — — — —
P1402 NG — NG NG
(Consecutive
NG)
(1st trip) DTC 1st trip DTC — 1st trip DTC
DTC
(= MIL ON)
SRT of EGR “INCMP” “INCMP” “INCMP” “CMPLT”
Revision: 2010 May2011 QX56