power steering INFINITI QX56 2009 Factory Repair Manual

EC-32
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AIR CONDITIONING CUT CONTROL
AIR CONDITIONING CUT CONTROL
Input/Output Signal ChartINFOID:0000000003771305
*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:0000000003771306
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 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.
Sensor Input Signal to ECM ECM function Actuator
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 sensor Refrigerant pressure
Power steering pressure sensor Power steering operation
Wheel sensor
Vehicle speed*
1
Revision: December 20092009 QX56

AUTOMATIC SPEED CONTROL DEVICE (ASCD)EC-33
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System DescriptionINFOID:0000000003771307
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 dr
iver 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 indicator 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 indi cator in combination meter illuminates.)
ACCELERATE OPERATION
If the RESUME/ACCELERATE switch is pressed during cruise 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 exist, cruise operation will be canceled.
 CANCEL switch is pressed
 More than 2 switches at ASCD steering 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 t he 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 function Actuator
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: December 20092009 QX56

EC-64
< FUNCTION DIAGNOSIS >[VK56DE]
ON BOARD DIAGNOSTIC (OBD) SYSTEM
ItemDIAGNOSTIC TEST MODE
WORK SUP-
PORT SELF-DIAGNOSTIC
RESULTS DATA
MONI-
TOR ACTIVE
TEST DTC & SRT
CONFIRMATION
DTC*1 FREEZE
FRAME
DATA*2 SRT
STATUS DTC
WORK
SUP-
PORT
ENGINE CONTROL COMPONENT PARTS
INPUT
Crankshaft position sensor (POS) ×××
Camshaft position sensor (PHASE) ×××
Mass air flow sensor ××
Engine coolant temperature sensor ××××
Air fuel ratio (A/F) sensor 1 ××××
Heated oxygen sensor 2 ××××
Wheel sensor ×××
Accelerator pedal position sensor ××
Throttle position sensor ×××
Fuel tank temperature sensor ×××
EVAP control system pressure sen-
sor ××
Intake air temperature sensor ×××
Knock sensor ×
Refrigerant pressure sensor ×
Closed throttle position switch (ac-
celerator pedal position sensor sig-
nal) ×
Air conditioner switch ×
Transmission range signal ××
Stop lamp switch ××
Power steering pressure sensor ××
Battery voltage ×
Load signal ×
Intake valve timing control position
sensor ××
Fuel level sensor ××
Battery current sensor ××
ICC steering switch ××
ASCD steering switch ××
ICC brake switch ××
ASCD brake switch ××
Revision: December 20092009 QX56

EC-68
< FUNCTION DIAGNOSIS >[VK56DE]
ON BOARD DIAGNOSTIC (OBD) SYSTEM
TP SEN 1-B1 [V]
××
 The throttle position sensor signal volt-
age is displayed.  TP SEN 2-B1 signal is converted by
ECM internally. Thus, it differs from
ECM terminal voltage signal.
TP SEN 2-B1 [V]
××
FUEL T/TMP SE
[ ° C] or [ °F]  The fuel temperature (determined by the
signal voltage of the fuel tank tempera-
ture sensor) is displayed.
INT/A TEMP SE
[ ° C] or [ °F] ××  The intake air temperature (determined
by the signal voltage of the intake air
temperature sensor) is indicated.
EVAP SYS PRES
[V]  The signal voltage of EVAP control sys-
tem pressure sensor is displayed.
FUEL LEVEL SE [V] × The signal voltage of the fuel level sen-
sor is displayed.
START SIGNAL
[ON/OFF]  Indicates start signal status [ON/OFF]
computed by the ECM according to the
signals of engine speed and battery volt-
age.  After starting the engine, [OFF] is dis-
played regardless of the starter signal.
CLSD THL POS
[ON/OFF] ×× Indicates idle position [ON/OFF] comput-
ed by ECM according to the accelerator
pedal position sensor signal.
AIR COND SIG
[ON/OFF] ×× Indicates [ON/OFF] condition of the air
conditioner switch as determined by the
air conditioner signal.
P/N POSI SW
[ON/OFF] ××
 Indicates [ON/OFF] condition from the
transmission range signal.
PW/ST SIGNAL
[ON/OFF] ×× [ON/OFF] condition of the power steering
system (determined by the signal voltage
of the power steering pressure sensor
signal) is indicated.
LOAD 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 lighting switch are OFF.
IGNITION SW
[ON/OFF] ×× Indicates [ON/OFF] condition from igni-
tion switch signal.
HEATER FAN SW
[ON/OFF] ×
 Indicates [ON/OFF] condition from heat-
er fan switch signal.
BRAKE SW
[ON/OFF]  Indicates [ON/OFF] condition from the
stop lamp switch signal.
INJ PULSE-B1
[msec]  Indicates the actual fuel injection pulse
width compensated by ECM according to
the input signals.  When the engine is stopped, a certain
computed value is indicated.
INJ PULSE-B2
[msec]
IGN TIMING [BT-
DC]  Indicates the ignition timing computed by
ECM according to the input signals.  When the engine is stopped, a certain
value is indicated.
CAL/LD VALUE [%]
 “Calculated load value” indicates the val- ue of the current air flow divided by peak
air flow.
MASS AIRFLOW
[g·m/s]  Indicates the mass air flow computed by
ECM according to the signal voltage of
the mass air flow sensor.
Monitored item
[Unit] ECM IN-
PUT SIG-
NALS MAIN
SIGNALS Description Remarks
Revision: December 20092009 QX56

TROUBLE DIAGNOSIS - SPECIFICATION VALUEEC-79
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OK >>
INSPECTION END
NG >> GO TO 15.
15.DISCONNECT AND RECONNECT ECM HARNESS CONNECTOR
1. Stop the engine.
2. Disconnect ECM harness connector. Check pin term inal and connector for damage, and then reconnect it.
>> GO TO 16.
16.CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”
1. Start engine.
2. Select “A/F ALPHA-B1”, “A/F AL PHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.
OK or NG
OK >> INSPECTION END
NG >> Detect malfunctioning part according to EC-475, "Symptom Matrix Chart"
.
17.CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” m ode, and make sure that the indication is within the
SP value.
OK or NG
OK >> INSPECTION END
NG (More than the SP value)>>GO TO 18.
NG (Less than the SP value)>>GO TO 25.
18.DETECT MALFUNCTIONING PART
1. Check for the cause of large engine friction. Refer to the following.
- Engine oil level is too high
- Engine oil viscosity
- Belt tension of power steering, alternator, A/C compressor, etc. is excessive
- Noise from engine
- Noise from transmission, etc.
2. Check for the cause of insufficient combustion. Refer to the following.
- Valve clearance malfunction
- Intake valve timing control function malfunction
- Camshaft sprocket installation malfunction, etc.
>> Repair or replace malfunctioning part, and then GO TO 30.
19.CHECK INTAKE SYSTEM
Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.
 Crushed air ducts
 Malfunctioning seal of air cleaner element
 Uneven dirt of air cleaner element
 Improper specification of intake air system
OK or NG
OK >> GO TO 21.
NG >> Repair or replace malfunctioning part, and then GO TO 20.
20.CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”, AND “B/FUEL SCHDL”
Select “A/F ALPHA-B1”, “A/F ALPHA-B2”, and “B/F UEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and
make sure that the each indication is within the SP value.
OK or NG
OK >> INSPECTION END
NG (“B/FUEL SCHDL” is more, “A/F ALPHA-B1”, “A /F ALPHA-B2” are less than the SP value)>>GO TO 21.
21.DISCONNECT AND RECONNECT MASS AIR FLOW SENSOR HARNESS CONNECTOR
1. Stop the engine.
Revision: December 20092009 QX56

P0506 ISC SYSTEMEC-273
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P0506 ISC SYSTEM
DescriptionINFOID:0000000003771546
NOTE:
If DTC P0506 is displayed with ot
her DTC, first perform the trouble diagnosis for the other DTC.
The ECM controls the engine idle speed to a specified leve l through the fine adjustment of the air, which is let
into the intake manifold, by operating the electric thrott le control actuator. The operating of the throttle valve is
varied to allow for optimum control of the engine idli ng speed. The crankshaft position sensor (POS) detects
the actual engine speed and sends a signal to the ECM.
The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value
memorized in the ECM. The target engine speed is t he lowest speed at which the engine can operate steadily.
The optimum value stored in the ECM is determined by taking into consideration various engine conditions,
such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan
operation, etc.).
On Board Diagnosis LogicINFOID:0000000003771547
DTC Confirmation ProcedureINFOID:0000000003771548
NOTE:
 If DTC Confirmation Procedure has been previously c onducted, always perform the following before con-
ducting the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
 If the target idle speed is ou t of the specified value, perform EC-18, "Idle Air Volume Learning"
,
before conducting DTC Confirmation Procedure. For the target idle speed, refer to the EC-495, "Idle
Speed and Ignition Timing".
TESTING CONDITION:
 Before performing the following procedure, confirm that battery voltage is more than 11V at idle.
 Always perform the test at a temperature above −10 °C (14 °F).
1. Open engine hood.
2. Start engine and warm it up to normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start engine and run it for at least 1 minute at idle speed.
5. Check 1st trip DTC.
6. If 1st trip DTC is detected, go to EC-273, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771549
1.CHECK INTAKE AIR LEAK
1. Start engine and let it idle.
2. Listen for an intake air leak after the mass air flow sensor.
OK or NG
OK >> GO TO 2.
NG >> Discover air leak location and repair.
2.REPLACE ECM
1. Stop engine.
2. Replace ECM.
3. Perform initialization of IVIS(NATS) system and regist ration of all IVIS(NATS) ignition key IDs. Refer to
SEC-6, "ECM RE-COMMUNICATING FUNCT ION : Special Repair Requirement"
.
4. Perform EC-17, "VIN Registration"
.
5. Perform EC-18, "Accelerator Pedal Released Position Learning"
.
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0506
0506 Idle speed control system
RPM lower than expected The idle speed is less than the target idle speed
by 100 rpm or more.  Electric throttle control actuator
 Intake air leak
Revision: December 20092009 QX56

P0507 ISC SYSTEMEC-275
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P0507 ISC SYSTEM
DescriptionINFOID:0000000003771550
NOTE:
If DTC P0507 is displayed with ot
her DTC, first perform the trouble diagnosis for the other DTC.
The ECM controls the engine idle speed to a specified leve l through the fine adjustment of the air, which is let
into the intake manifold, by operating the electric thrott le control actuator. The operating of the throttle valve is
varied to allow for optimum control of the engine idli ng speed. The crankshaft position sensor (POS) detects
the actual engine speed and sends a signal to the ECM.
The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value
memorized in the ECM. The target engine speed is t he lowest speed at which the engine can operate steadily.
The optimum value stored in the ECM is determined by taking into consideration various engine conditions,
such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan
operation, etc.).
On Board Diagnosis LogicINFOID:0000000003771551
DTC Confirmation ProcedureINFOID:0000000003771552
NOTE:
 If DTC Confirmation Procedure has been previously c onducted, always perform the following before con-
ducting the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
 If the target idle speed is ou t of the specified value, perform EC-18, "Idle Air Volume Learning"
,
before conducting DTC Confirmation Procedure. For the target idle speed, refer to the EC-495, "Idle
Speed and Ignition Timing".
TESTING CONDITION:
 Before performing the following procedure, confirm that battery voltage is more than 11V at idle.
 Always perform the test at a temperature above −10 °C (14 °F).
1. Open engine hood.
2. Start engine and warm it up to normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start engine and run it for at least 1 minute at idle speed.
5. Check 1st trip DTC.
6. If 1st trip DTC is detected, go to EC-275, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771553
1.CHECK PCV HOSE CONNECTION
Confirm that PCV hose is connected correctly.
OK or NG
OK >> GO TO 2.
NG >> Repair or replace.
2.CHECK INTAKE AIR LEAK
1. Start engine and let it idle.
2. Listen for an intake air leak after the mass air flow sensor.
OK or NG
OK >> GO TO 3.
NG >> Discover air leak location and repair.
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0507
0507 Idle speed control system
RPM higher than expected The idle speed is more than the target idle
speed by 200 rpm or more.  Electric throttle control actuator
 Intake air leak
 PCV system
Revision: December 20092009 QX56

P0550 PSP SENSOREC-277
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P0550 PSP SENSOR
Component DescriptionINFOID:0000000003771554
Power steering pressure (PSP) sensor (1) 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.
On Board Diagnosis LogicINFOID:0000000003771555
The MIL will not light up for this self-diagnosis.
NOTE:
If DTC P0550 is displayed with DTC P0643, first pe rform the trouble diagnosis for DTC P0643. Refer to
EC-285
.
DTC Confirmation ProcedureINFOID:0000000003771556
1. If DTC Confirmation Procedure has been previously c onducted, always perform the following before con-
ducting the next step.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Turn ignition switch ON.
c. Turn ignition switch OFF and wait at least 10 seconds.
2. Start engine and let it idle for at least 5 seconds.
3. Check 1st trip DTC.
4. If 1st trip DTC is detected, go to EC-277, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771557
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body. Refer to EC-85, "Ground Inspection"
.
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
BBIA0741E
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0550
0550 Power steering pressure
sensor circuit An excessively low or high voltage from the
sensor is sent to ECM.  Harness or connectors
(The sensor circuit is open or shorted)
 Power steering pressure sensor
BBIA0354E
Revision: December 20092009 QX56

EC-278
< COMPONENT DIAGNOSIS >[VK56DE]
P0550 PSP SENSOR
2.CHECK PSP SENSOR POWER SUPPLY CIRCUIT
1. Disconnect power steering pressure (PSP) sensor (1) harness connector.
2. Turn ignition switch ON.
3. Check voltage between PSP sensor terminal 1 and ground with CONSULT-III or tester.
OK or NG
OK >> GO TO 3.
NG >> Repair harness or connectors.
3.CHECK PSP SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between PSP sensor terminal 3 and ECM terminal 67. Refer to Wiring Diagram.
4. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 4.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
4.CHECK PSP SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between ECM terminal 12 and PSP sensor terminal 2.
2. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 5.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
5.CHECK PSP SENSOR
Refer to EC-279, "Component Inspection"
.
OK or NG
OK >> GO TO 6.
NG >> Replace PSP sensor.
6.CHECK INTERMITTENT INCIDENT
Refer to GI-35, "How to Check Terminal"
and GI-38, "Intermittent Incident".
>> INSPECTION END
BBIA0741E
Voltage: Approximately 5V
PBIB0188E
Continuity should exist.
Continuity should exist.
Revision: December 20092009 QX56

P0550 PSP SENSOREC-279
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Component InspectionINFOID:0000000003771558
POWER STEERING PRESSURE SENSOR
1. Reconnect all harness connectors disconnected.
2. Start engine and let it idle.
3. Check voltage between ECM terminal 12 and ground under the
following conditions.
Condition Voltage
Steering wheel: Being turned. 0.5 - 4.5V
Steering wheel: Not being turned. 0.4 - 0.8V
MBIB0126E
Revision: December 20092009 QX56