brake sensor INFINITI QX56 2011 Factory Service Manual
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![INFINITI QX56 2011  Factory Service Manual 
DLN-18
< SYSTEM DESCRIPTION >[TRANSFER: ATX90A]
SYSTEM
SYSTEM
4WD SYSTEM
4WD SYSTEM : System DescriptionINFOID:0000000006222224
 In AUTO mode, distribution of traction force is cont
rolled from 2WD  INFINITI QX56 2011  Factory Service Manual 
DLN-18
< SYSTEM DESCRIPTION >[TRANSFER: ATX90A]
SYSTEM
SYSTEM
4WD SYSTEM
4WD SYSTEM : System DescriptionINFOID:0000000006222224
 In AUTO mode, distribution of traction force is cont
rolled from 2WD](/img/42/57033/w960_57033-1819.png)
DLN-18
< SYSTEM DESCRIPTION >[TRANSFER: ATX90A]
SYSTEM
SYSTEM
4WD SYSTEM
4WD SYSTEM : System DescriptionINFOID:0000000006222224
 In AUTO mode, distribution of traction force is cont
rolled from 2WD status (0:100) to 4WD status (50:50)
according to signal from each sensor and switch.
 In accordance with fail-safe function, when system is malfunctioning, 4WD warning lamp on combination meter turns ON and 4WD control stops. For fail-safe function, refer to  DLN-20, "
4WD SYSTEM : Fail-Safe".
 When a high load status continues for transfer assembly  (transfer control actuator or transfer fluid), 4WD
control temporarily becomes 4H or 2WD  status, according to protection function.
NOTE:
4WD system is not malfunctioning.
SYSTEM DIAGRAM
INPUT/OUTPUT SIGNAL
It transmits/receives each signal from the followi ng transfer control unit via CAN communication line.
JPDIE0272GB
Component parts Control signal
ABS actuator and electric unit (control unit) Transmits the following signals via CAN communication line to transfer control unit.
 Vehicle spee
d signal (ABS)
 Stop lamp switch signal (brake signal)
 ABS operation signal
 VDC operation signal
 TCS operation signal
ECM Transmits the following signals via CAN communication line to transfer control unit.
 Accelerator pedal position signal
 Engine speed signal
 Engine torque signal
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4WD SHIFT SWITCH AND 4WD SHIFT INDICATOR LAMP
*1: Blinking 2 times/1 second
*2: “4HI” and “4LO” blink a INFINITI QX56 2011  Factory Service Manual 
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< SYSTEM DESCRIPTION > [TRANSFER: ATX90A]
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4WD SHIFT SWITCH AND 4WD SHIFT INDICATOR LAMP
*1: Blinking 2 times/1 second
*2: “4HI” and “4LO” blink a](/img/42/57033/w960_57033-1820.png)
SYSTEMDLN-19
< SYSTEM DESCRIPTION > [TRANSFER: ATX90A]
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4WD SHIFT SWITCH AND 4WD SHIFT INDICATOR LAMP
*1: Blinking 2 times/1 second
*2: “4HI” and “4LO” blink alternately.
CONDITION FOR TURN ON THE WARNING LAMP
TCM Transmits the following signals via CAN communication line to transfer control unit.
 Shift position signal
 Gear position signal
 Output shaft revolution signal
Steering angle sensor Transmits the following signals via CAN communication line to transfer control unit.
 Steering angle sensor signal
Combination meter  Receives the following signals via CAN communication line from transfer control unit.
 4WD warning lamp signal
 ATP warning lamp signal
 4WD mode indicator signal
Component parts Control signal
4WD shift switch 4WD shift indicator lamp (in Information display) 4WD shift procedure
AUTO
1. Start the engine.
2. Turn the 4WD shift switch.
NOTE:
Mode can be switched between AU-
TO⇔4H while driving straight.
4H
↓↑
4WD status: 4H ⇔4L (Blinking)
*1*2
1. Start the engine.
2. Never drive the vehicle.
3. Shift A/T shift selector to N position.
4. Press and rotate 4WD shift switch 
while depressing brake pedal.
CAUTION:
4WD mode does not switch when 4WD 
shift switch is operated while the vehi-
cle is running or A/T shift selector is 
shifted to any position other than neu-
tral.
4L
JPDIE0230ZZJPDIE0234ZZ
JPDIE0231ZZJPDIE0235ZZ
JPDIE0231ZZ
JPDIE0233ZZ
JPDIE0236ZZ
JPDIE0233ZZJPDIE0237ZZ
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EC-1
ENGINE
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CONTENTS
ENGINE CONTROL SYSTEM
VK56VD
PRECAUTION ................ ...............................
9
PRECAUTIONS .............................................. .....9
Precaution for Supplemental Restraint System 
(SRS) "AIR BAG" and "SEAT BELT PRE-TEN-
SIONER" ............................................................. ......
9
Precaution for Procedure without Cowl Top Cover ......9
Precautions For Xenon Headlamp Service  ...............9
On Board Diagnostic (OBD) System of Engine 
and A/T ....................................................................
10
General Precautions  ...............................................10
PREPARATION ...........................................14
PREPARATION .............................................. ....14
Special Service Tools .......................................... ....14
Commercial Service Tools  ......................................14
SYSTEM DESCRIPTION  .............................16
COMPONENT PARTS  ................................... ....16
Component Parts Location .................................. ....16
Component Description ...........................................19
Accelerator Pedal Position Sensor ..........................21
Air Fuel Ratio (A/F) Sensor 1  ..................................21
ASCD Brake Switch & Stop Lamp Switch  ...............21
ASCD Steering Switch  ............................................21
ASCD Indicators ......................................................21
Battery Current Sensor (With Battery Tempera-
ture Sensor)  ............................................................
22
Camshaft Position Sensor .......................................22
Crankshaft Position Sensor .....................................23
ECM ........................................................................23
Electric Throttle Control Actuator  ............................23
Electrically-controlled cooling fan coupling  .............24
Engine Coolant Temperature Sensor ......................25
Engine Oil Temperature Sensor ..............................25
EVAP Control System Pressure Sensor  .................26
EVAP Canister Vent Control Valve  .........................26
EVAP Canister Purge Volume Control Solenoid 
Valve .................................................................... ....
26
Fuel Injector  .............................................................26
Fuel Level Sensor ....................................................26
Fuel Pump Control Module  ......................................27
Fuel Rail Pressure Sensor .......................................27
Fuel Tank Temperature Sensor ...............................27
Heated Oxygen Sensor 2  ........................................27
High Pressure Fuel Pump  .......................................28
ICC Brake Switch & Stop Lamp Switch  ...................29
ICC Steering Switch  ................................................29
Ignition Coil With Power Transistor  .........................29
Intake Valve Timing Control Solenoid Valve  ...........29
Knock Sensor  ...................................................... ....30
Low Fuel Pressure Sensor  ......................................30
Low Pressure Fuel Pump  ........................................30
Malfunction Indicator Lamp (MIL)  ............................30
Manifold Absolute Pressure Sensor  ........................31
Mass Air Flow Sensor (With Intake Air Tempera-
ture Sensor)  .............................................................
31
Power Steering Pressure (PSP) Sensor ..................31
Refrigerant Pressure Sensor  ............................... ....32
VVEL Actuator Motor  ...............................................32
VVEL Actuator Motor Relay .....................................32
VVEL Control Module  ..............................................32
VVEL Control Shaft Position Sensor  .......................32
STRUCTURE AND OPERATION  .....................33
Positive Crankcase Ventilation  ................................33
On Board Refueling Vapor Recovery (ORVR)  ........34
SYSTEM ............................................................35
ENGINE CONTROL SYSTEM  ........................ ...........35
ENGINE CONTROL SYSTEM : System Diagram  ....35
ENGINE CONTROL SYSTEM : System Descrip-
tion ...........................................................................
35
DIRECT INJECTION GASOLINE SYSTEM  .......... ....36
DIRECT INJECTION GASOLINE SYSTEM : 
System Diagram .....................................................
36
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EC-7
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P1553 BATTERY CURRENT SENSOR  ......... ..420
DTC Logic  ........................................................... ..420
Diagnosis Procedure  .............................................420
Component Inspection (Battery Current Sensor) ..423
P1554 BATTERY CURRENT SENSOR  ...........424
DTC Logic  ........................................................... ..424
Component Function Check ..................................424
Diagnosis Procedure  .............................................425
Component Inspection (Battery Current Sensor) ..427
P1556, P1557 BATTERY TEMPERATURE 
SENSOR ...........................................................
428
DTC Logic  ........................................................... ..428
Diagnosis Procedure  .............................................428
Component Inspection (Battery Temprature Sen-
sor) ........................................................................
430
P1564 ASCD STEERING SWITCH  ..................431
DTC Logic  ........................................................... ..431
Diagnosis Procedure  .............................................431
Component Inspection (ASCD Steering Switch)  ...433
P1564 ICC STEERING SWITCH  ......................434
DTC Logic  ........................................................... ..434
Diagnosis Procedure  .............................................434
Component Inspection (ICC Steering Switch) .......436
P1568 ICC FUNCTION  .....................................437
DTC Logic  ........................................................... ..437
Diagnosis Procedure  .............................................437
P1572 ASCD BRAKE SWITCH  .......................438
DTC Logic  ........................................................... ..438
Diagnosis Procedure  .............................................439
Component Inspection (ASCD Brake Switch)  .......442
Component Inspection (Stop Lamp Switch)  ..........442
P1572 ICC BRAKE SWITCH  ...........................443
DTC Logic  ........................................................... ..443
Diagnosis Procedure  .............................................444
Component Inspection (ICC Brake Switch) ...........445
Component Inspection (Stop Lamp Switch)  ..........446
P1574 ASCD VEHICLE SPEED SENSOR  ......447
Description .......................................................... ..447
DTC Logic  .............................................................447
Diagnosis Procedure  .............................................447
P1574 ICC VEHICLE SPEED SENSOR  ..........449
Description .......................................................... ..449
DTC Logic  .............................................................449
Diagnosis Procedure  .............................................449
P1606 VVEL CONTROL MODULE  ..................451
DTC Logic  ........................................................... ..451
Diagnosis Procedure  .............................................451
P1607 VVEL CONTROL MODULE  ..................452
DTC Logic  ........................................................... ..452
Diagnosis Procedure  .............................................452
P1608 VVEL SENSOR POWER SUPPLY  ......453
DTC Logic ............................................................ ..453
Diagnosis Procedure  .............................................453
P1805 BRAKE SWITCH  .................................455
DTC Logic ..............................................................455
Diagnosis Procedure  .............................................455
Component Inspection (Stop Lamp Switch)  ..........456
P2100, P2103 THROTTLE CONTROL MO-
TOR RELAY  ....................................................
458
DTC Logic ..............................................................458
Diagnosis Procedure  .............................................458
P2101 ELECTRIC THROTTLE CONTROL 
FUNCTION ......................................................
460
Description ........................................................... ..460
DTC Logic ..............................................................460
Diagnosis Procedure  .............................................460
Component Inspection ...........................................462
Special Repair Requirement ..................................463
P2118 THROTTLE CONTROL MOTOR  .........464
DTC Logic ..............................................................464
Diagnosis Procedure  .............................................464
Component Inspection (Electric Throttle Control 
Motor) ....................................................................
465
P2119 ELECTRIC THROTTLE CONTROL 
ACTUATOR .....................................................
466
DTC Logic ..............................................................466
Diagnosis Procedure  .............................................466
P2122, P2123 APP SENSOR  .........................468
DTC Logic ..............................................................468
Diagnosis Procedure  .............................................468
Component Inspection (Accelerator Pedal Posi-
tion Sensor)  ...........................................................
470
P2127, P2128 APP SENSOR  .........................471
DTC Logic ..............................................................471
Diagnosis Procedure  .............................................471
Component Inspection (Accelerator Pedal Posi-
tion Sensor)  ...........................................................
474
P2135 TP SENSOR .........................................475
DTC Logic ..............................................................475
Diagnosis Procedure  .............................................475
Component Inspection (Throttle Position Sensor) ..476
P2138 APP SENSOR  ......................................478
DTC Logic ..............................................................478
Diagnosis Procedure  .............................................478
Component Inspection (Accelerator Pedal Posi-
tion Sensor)  ...........................................................
481
P2539, P2541, P2542 LOW FUEL PRES-
SURE SENSOR ...............................................
483
DTC Logic ..............................................................483
Diagnosis Procedure  .............................................483
Component Inspection ...........................................485
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EC-8
P2A00, P2A03 A/F SENSOR 1  .......................487
DTC Logic ............................................................ ..487
Diagnosis Procedure  .............................................487
ASCD BRAKE SWITCH ................................. .490
Component Function Check  ................................ ..490
Diagnosis Procedure  .............................................490
Component Inspection (ASCD Brake Switch)  .......491
ASCD INDICATOR  ..........................................492
Component Function Check  ................................ ..492
Diagnosis Procedure  .............................................492
ELECTRICAL LOAD SIGNAL  .........................493
Description ........................................................... ..493
Component Function Check  ..................................493
Diagnosis Procedure  .............................................493
ELECTRICALLY-CONTROLLED COOLING 
FAN COUPLING  ..............................................
495
Component Function Check  ................................ ..495
Diagnosis Procedure  .............................................495
FUEL INJECTOR  .............................................498
Component Function Check  ................................ ..498
Diagnosis Procedure  .............................................498
Component Inspection ...........................................499
HIGH PRESSURE FUEL PUMP  ......................501
Component Function Check  ................................ ..501
Diagnosis Procedure  .............................................501
Component Inspection ...........................................502
ICC BRAKE SWITCH  ......................................503
Component Function Check  ................................ ..503
Diagnosis Procedure  .............................................503
Component Inspection (ICC Brake Switch)  ...........505
IGNITION SIGNAL  ...........................................506
Component Function Check  ................................ ..506
Diagnosis Procedure  .............................................506
Component Inspection (Ignition Coil with Power 
Transistor) .............................................................
509
Component Inspection (Condenser)  ......................510
INFORMATION DISPLAY (ASCD)  ..................511
Component Function Check  ................................ ..511
Diagnosis Procedure  .............................................511
LOW PRESSURE FUEL PUMP  ......................512
Component Function Check  ................................ ..512
Diagnosis Procedure  .............................................512
Component Inspection (Low Pressure Fuel Pump) 
..
513
Component Inspection (FPCM)  .............................514
MALFUNCTION INDICATOR LAMP  ...............515
Component Function Check  ................................ ..515
Diagnosis Procedure  .............................................515
ON BOARD REFUELING VAPOR RECOV-
ERY (ORVR)  .....................................................
516
Component Function Check  ................................ .516
Diagnosis Procedure .............................................516
Component Inspection (EVAP Vapor Cut Valve)  . .518
REFRIGERANT PRESSURE SENSOR  ......... ..520
Component Function Check  ................................ .520
Diagnosis Procedure .............................................520
SNOW MODE SWITCH  ....................................522
Description ........................................................... .522
Component Function Check  .................................522
Diagnosis Procedure .............................................522
Component Inspection  ..........................................523
SYMPTOM DIAGNOSIS  ...........................524
ENGINE CONTROL SYSTEM SYMPTOMS  .. ..524
Symptom Table  .................................................... .524
NORMAL OPERATING CONDITION  ...............529
Description ........................................................... .529
PERIODIC MAINTENANCE ......................530
IDLE SPEED  .......................... ...........................530
Inspection ............................................................. .530
IGNITION TIMING .............................................531
Inspection ............................................................. .531
EVAP LEAK CHECK  ........................................532
Inspection ............................................................. .532
POSITIVE CRANKCASE VENTILATION .........534
Inspection ............................................................. .534
REMOVAL AND INSTALLATION .............535
ECM ................................................................ ..535
Removal and Installation ...................................... .535
VVEL CONTROL MODULE  .............................536
Removal and Installation ...................................... .536
FUEL PUMP CONTROL MODULE (FPCM)  ....537
Removal and Installation ...................................... .537
SERVICE DATA AND SPECIFICATIONS 
(SDS) ........ .................................................
538
SERVICE DATA AND SPECIFICATIONS 
(SDS) .............................................................. ..
538
Idle Speed  ............................................................ .538
Ignition Timing .......................................................538
Calculated Load Value  ..........................................538
Mass Air Flow Sensor  ...........................................538
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< SYSTEM DESCRIPTION > [VK56VD]
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Component DescriptionINFOID:0000000006217657
1. ASCD steering switch
ICC steering switch 2. Snow mode switch 3. Fu INFINITI QX56 2011  Factory Service Manual 
COMPONENT PARTSEC-19
< SYSTEM DESCRIPTION > [VK56VD]
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Component DescriptionINFOID:0000000006217657
1. ASCD steering switch
ICC steering switch 2. Snow mode switch 3. Fu](/img/42/57033/w960_57033-2042.png)
COMPONENT PARTSEC-19
< SYSTEM DESCRIPTION > [VK56VD]
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Component DescriptionINFOID:0000000006217657
1. ASCD steering switch
ICC steering switch 2. Snow mode switch 3. Fuel level sensor unit and fuel pump 
assembly (with fuel tank temperature 
sensor)
4. Fuel pump control module (FPCM) 5. EVAP canister vent control valve 6. EVAP canister
7. EVAP control system pressure sen- sor 8. Stop lamp switch 9. ASCD brake switch
ICC brake switch
10. Accelerator pedal position sensor
JSBIA0606ZZ
Component Reference
ECM EC-23, "
ECM"
Malfunction indicator lamp (MIL)EC-30, "Malfunction Indicator Lamp (MIL)"
Ignition coil with power transistorEC-29, "Ignition Coil With Power Transistor"
Accelerator pedal position sensorEC-21, "Accelerator Pedal Position Sensor"
Mass air flow sensor
EC-31, "Mass Air Flow Sensor (With Intake Air Temperature Sen-
sor)"Intake air temperature sensor
Electric throttle control actuator
EC-23, "
Electric Throttle Control Actuator"Throttle control motor relay
Throttle control motor
Throttle position sensor
Crankshaft position sensorEC-23, "
Crankshaft Position Sensor"
Camshaft position sensorEC-22, "Camshaft Position Sensor"
Engine coolant temperature sensorEC-25, "Engine Coolant Temperature Sensor"
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EC-20
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
High pressure fuel pump
EC-28, "High Pressure Fuel Pump"
Low pressure fuel pumpEC-30, "Low Pressure Fuel Pump"
Fuel pump control module (FPCM)EC-2 INFINITI QX56 2011  Factory Service Manual 
EC-20
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
High pressure fuel pump
EC-28, "High Pressure Fuel Pump"
Low pressure fuel pumpEC-30, "Low Pressure Fuel Pump"
Fuel pump control module (FPCM)EC-2](/img/42/57033/w960_57033-2043.png)
EC-20
< SYSTEM DESCRIPTION >[VK56VD]
COMPONENT PARTS
High pressure fuel pump
EC-28, "High Pressure Fuel Pump"
Low pressure fuel pumpEC-30, "Low Pressure Fuel Pump"
Fuel pump control module (FPCM)EC-27, "Fuel Pump Control Module"
Fuel rail pressure sensorEC-27, "Fuel Rail Pressure Sensor"
Low fuel pressure sensorEC-30, "Low Fuel Pressure Sensor"
Fuel injectorEC-26, "Fuel Injector"
Fuel level sensorEC-26, "Fuel Level Sensor"
Fuel tank temperature sensorEC-27, "Fuel Tank Temperature Sensor"
A/F sensor 1
EC-21, "Air Fuel Ratio (A/F) Sensor 1"A/F sensor 1 heater
Heated oxygen sensor 2EC-27, "
Heated Oxygen Sensor 2"Heated oxygen sensor 2 heater
Manifold absolute pressure sensorEC-31, "
Manifold Absolute Pressure Sensor"
Knock sensorEC-30, "Knock Sensor"
Engine oil temperature sensorEC-25, "Engine Oil Temperature Sensor"
Power steering pressure sensorEC-31, "Power Steering Pressure (PSP) Sensor"
Electrically-controlled cooling fan coupling EC-24, "Electrically-controlled cooling fan coupling"
Intake valve timing control solenoid valveEC-29, "Intake Valve Timing Control Solenoid Valve"
VVEL control moduleEC-32, "VVEL Control Module"
VVEL actuator motor relayEC-32, "VVEL Actuator Motor Relay"
VVEL actuator motorEC-32, "VVEL Actuator Motor"
VVEL control shaft position sensor EC-32, "VVEL Control Shaft Position Sensor"
EVAP control system pressure sensor EC-26, "EVAP Control System Pressure Sensor"
EVAP canister vent control valveEC-26, "EVAP Canister Vent Control Valve"
EVAP canister purge volume control solenoid valveEC-26, "EVAP Canister Purge Volume Control Solenoid Valve"
Battery current sensor (with battery temperature sensor)EC-22, "Battery Current Sensor (With Battery Temperature Sen-
sor)"
Refrigerant pressure sensor
EC-32, "Refrigerant Pressure Sensor"
Stop lamp switch
EC-21, "ASCD Brake Switch & Stop Lamp Switch"ASCD brake switch
ASCD steering switchEC-21, "
ASCD Steering Switch"
Information displayEC-49, "AUTMATIC SPEED CONTROL DEVICE (ASCD) : Switch 
Name and Function"
Stop lamp switch
EC-29, "ICC Brake Switch & Stop Lamp Switch"ICC brake switch
ICC steering switchEC-29, "
ICC Steering Switch"
Component Reference
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< SYSTEM DESCRIPTION > [VK56VD]
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Accelerator Pedal 
Position SensorINFOID:0000000006217658
The accelerator pedal position (APP) sensor is installed INFINITI QX56 2011  Factory Service Manual 
COMPONENT PARTSEC-21
< SYSTEM DESCRIPTION > [VK56VD]
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Accelerator Pedal 
Position SensorINFOID:0000000006217658
The accelerator pedal position (APP) sensor is installed](/img/42/57033/w960_57033-2044.png)
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
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EC-48
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
AUTOMATIC SPEED CONTROL DEVI CE (ASCD) : System Diagram
INFOID:0000000006217715
AUTOMATIC SPEED CONTROL DEVICE  (ASCD) : System DescriptionINFOID:000000000 INFINITI QX56 2011  Factory Service Manual 
EC-48
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
AUTOMATIC SPEED CONTROL DEVI CE (ASCD) : System Diagram
INFOID:0000000006217715
AUTOMATIC SPEED CONTROL DEVICE  (ASCD) : System DescriptionINFOID:000000000](/img/42/57033/w960_57033-2071.png)
EC-48
< SYSTEM DESCRIPTION >[VK56VD]
SYSTEM
AUTOMATIC SPEED CONTROL DEVI CE (ASCD) : System Diagram
INFOID:0000000006217715
AUTOMATIC SPEED CONTROL DEVICE  (ASCD) : System DescriptionINFOID:0000000006217716
INPUT/OUTPUT SIGNAL CHART
*: This signal is sent to the ECM via the CAN communication line
BASIC ASCD SYSTEM
 Automatic Speed Control Device (ASCD) allows a dr iver to keep vehicle at predetermined constant speed
without depressing accelerator pedal. Driver can be set the vehicle speed in the set speed range.
 ECM controls throttle angle of electric th rottle control actuator to regulate engine speed.
 Operation status of ASCD is indicated in combination meter.
 If any malfunction occurs in the ASCD system,  it automatically deactivates the ASCD control.
Refer to  EC-49, "
AUTMATIC SPEED CONTROL DEVICE (A SCD) : Switch Name and Function" for ASCD
operating instructions.
CAUTION:
Always drive vehicle in a safe manner according to  traffic conditions and obey all traffic laws.
CAN COMMUNICATION
CAN COMMUNICATION : System DescriptionINFOID:0000000006217718
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 s peed 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 CA N 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-28, "
CAN COMMUNICATION SYSTEM :  CAN Communication Signal Chart", about CAN com-
munication for detail.
JPBIA3272GB
Sensor Input signal to ECM ECM function Actuator
ASCD steering switch ASCD steering switch operation
ASCD vehicle speed control Electric throttle control ac-
tuator 
 Combination meter
ASCD brake switch
Brake pedal operation
Sto p l am p s w it ch
TCM Park/neutral position signal
Output shaft revolution signal*
Combination meter Vehicle speed signal*
Revision: 2010 May2011 QX56  
Page 2091 of 5598
![INFINITI QX56 2011  Factory Service Manual 
DIAGNOSIS SYSTEM (ECM)EC-67
< SYSTEM DESCRIPTION > [VK56VD]
C
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G H
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M A
EC
NP
OLOAD SIGNAL ON/OFF
 Indicates [ON/OFF] condition from the electrical 
load signal.
ON: Rear window defogger INFINITI QX56 2011  Factory Service Manual 
DIAGNOSIS SYSTEM (ECM)EC-67
< SYSTEM DESCRIPTION > [VK56VD]
C
D
E
F
G H
I
J
K L
M A
EC
NP
OLOAD SIGNAL ON/OFF
 Indicates [ON/OFF] condition from the electrical 
load signal.
ON: Rear window defogger](/img/42/57033/w960_57033-2090.png)
DIAGNOSIS SYSTEM (ECM)EC-67
< SYSTEM DESCRIPTION > [VK56VD]
C
D
E
F
G H
I
J
K L
M A
EC
NP
OLOAD SIGNAL ON/OFF
 Indicates [ON/OFF] condition from the electrical 
load signal.
ON: Rear window defogger switch is ON and/or 
lighting switch is in 2nd position.
OFF: Both rear window defogger switch and light-
ing switch are OFF.
IGNITION SW ON/OFF  Indicates [ON/OFF] condition from ignition switch 
signal.
HEATER FAN SW ON/OFF  Indicates [ON/OFF] condition from the blower fan 
ON signal.
BRAKE SW ON/OFF  Indicates [ON/OFF] condition from the stop lamp 
switch signal.
IGN TIMING BTDC  Indicates the ignition timing computed by ECM ac-
cording to the input signals.  When the engine is stopped, 
a certain value is indicated.
COMBUSTION —  These items are displayed but are not applicable to 
this model.
CAL/LD VALUE %  “Calculated load value” indicates the value of the 
current air flow divided by peak air flow.
MASS AIRFLOW g/s  Indicates the mass air flow computed by ECM ac-
cording to the signal voltage of the mass air flow 
sensor.
PURG VOL C/V %  Indicates the EVAP canister purge volume control 
solenoid valve control value computed by the ECM 
according to the input signals.
 The opening becomes larger as the value increas-
es.
INT/V SOL (B1)
% The control value of the intake valve timing control 
solenoid valve (determined by ECM according to 
the input signals) is indicated.
 The advance angle becomes larger as the value  increases.
INT/V SOL (B2)
AIR COND RLY ON/OFF
 The air conditioner relay control condition (deter-
mined by ECM according to the input signals) is in-
dicated.
VENT CONT/V ON/OFF  The control condition of the EVAP canister vent 
control valve (determined by ECM according to the 
input signals) is indicated.
ON: Closed
OFF: Open
THRTL RELAY ON/OFF  Indicates the throttle co
ntrol motor relay control 
condition determined by the ECM according to the 
input signals.
A/F S1 HTR (B1)
% Air fuel ratio (A/F) sensor 1 heater control value 
computed by ECM according to the input signals.
 The current flow to the heater becomes larger as  the value increases.
A/F S1 HTR (B2)
HO2S2 HTR (B1)
ON/OFF Indicates [ON/OFF] condition of heated oxygen 
sensor 2 heater determined by ECM according to 
the input signals.
HO2S2 HTR (B2)
ALT DUTY SIG ON/OFF  The control condition of the power generation volt-
age variable control (determined by ECM accord-
ing to the input signals) is indicated.
ON: Power generation voltage variable control is 
active.
OFF: Power generation voltage variable control is 
inactive.
I/P PULLY SPD rpm  Indicates the engine speed computed from the in-
put speed sensor signal.
Monitored item Unit Description Remarks
Revision: 2010 May2011 QX56