2004 INFINITI QX56 Engine Control System

DTC P1444 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
EC-497
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On Board Diagnosis LogicUBS00HAV
DTC Confirmation ProcedureUBS00HAW
NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
TESTING CONDITION:
Always perform test at a temperature of 5°C (41°F) or more.
WITH CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Select “PURG VOL CN/V P1444” of “EVAPORATIVE SYSTEM” in “DTC WORK SUPPORT” mode with
CONSULT-II.
5. Touch “START”.
6. Start engine and let it idle until “TESTING” on CONSULT-II changes to “COMPLETED”. (It will take
approximately 10 seconds.)
If “TESTING” is not displayed after 5 minutes, retry from step 2.
7. Make sure that “OK” is displayed after touching “SELF-DIAG RESULTS”. If “NG” is displayed, refer to EC-
500, "Diagnostic Procedure" .
WITH GST
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and let it idle for at least 20 seconds.
4. Select MODE 7 with GST.
5. If 1st trip DTC is detected, go to EC-500, "
Diagnostic Procedure" .
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1444
1444EVAP canister purge
volume control solenoid
valveThe canister purge flow is detected during the
specified driving conditions, even when EVAP
canister purge volume control solenoid valve is
completely closed.

EVAP control system pressure sensor

EVAP canister purge volume control
solenoid valve
(The valve is stuck open.)

EVAP canister vent control valve

EVAP canister

Hoses
(Hoses are connected incorrectly or
clogged.)
PBIB0839E

DTC P1444 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
EC-501
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4. CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR CONNECTOR
1. Disconnect EVAP control system pressure sensor harness connector.
2. Check connectors for water.
OK or NG
OK >> GO TO 5.
NG >> Replace EVAP control system pressure sensor.
5. CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR
Refer to EC-301, "
Component Inspection" .
OK or NG
OK (With CONSULT-II)>>GO TO 6.
OK (Without CONSULT-II)>>GO TO 7.
NG >> Replace EVAP control system pressure sensor.
6. CHECK EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
With CONSULT-II
1. Turn ignition switch OFF.
2. Reconnect all harness connectors disconnected.
3. Start engine.
4. Perform “PURG VOL CONT/V” in “ACTIVE TEST” mode with
CONSULT-II. Check that engine speed varies according to the
valve opening.
OK or NG
OK >> GO TO 8.
NG >> GO TO 7.
7. CHECK EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
Refer to EC-503, "
Component Inspection" .
OK or NG
OK >> GO TO 8.
NG >> Replace EVAP canister purge volume control solenoid valve.
8. CHECK RUBBER TUBE FOR CLOGGING
1. Disconnect rubber tube connected to EVAP canister vent control valve.
2. Check the rubber tube for clogging.
OK or NG
OK >> GO TO 9.
NG >> Clean the rubber tube using an air blower.
9. CHECK EVAP CANISTER VENT CONTROL VALVE
Refer to EC-297, "
Component Inspection" .
OK or NG
OK >> GO TO 10.
NG >> Replace EVAP canister vent control valve.Water should not exist.
PBIB1678E

FUEL PUMP CIRCUIT
EC-601
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FUEL PUMP CIRCUITPFP:17042
DescriptionUBS00HDB
SYSTEM DESCRIPTION
*: ECM determines the start signal status by the signals of engine speed and battery voltage.
The ECM activates the fuel pump for several seconds after the ignition switch is turned ON to improve engine
startability. If the ECM receives a engine speed signal from the camshaft position sensor (PHASE), it knows
that the engine is rotating, and causes the pump to operate. If the engine speed signal is not received when
the ignition switch is ON, the engine stalls. The ECM stops pump operation and prevents battery discharging,
thereby improving safety. The ECM does not directly drive the fuel pump. It controls the ON/OFF fuel pump
relay, which in turn controls the fuel pump.
COMPONENT DESCRIPTION
A turbine type design fuel pump is used in the furl tank.
CONSULT-II Reference Value in Data Monitor ModeUBS00HDC
Specification data are reference values.
Sensor Input signal to ECM ECM Function Actuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)Engine speed*
Fuel pump control Fuel pump relay
Battery Battery voltage*
Condition Fuel pump operation
Ignition switch is turned to ON. Operates for 1 second.
Engine running and crankingOperates.
When engine is stoppedStops in 1.5 seconds.
Except as shown aboveSto ps.
BBIA0402E
MONITOR ITEM CONDITION SPECIFICATION
FUEL PUMP RLY

For 1 second after turning ignition switch ON

Engine running or crankingON

Except above conditions OFF

EVAPORATIVE EMISSION SYSTEM
EC-633
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EVAPORATIVE EMISSION SYSTEMPFP:14950
DescriptionUBS00HDY
SYSTEM DESCRIPTION
The evaporative emission system is used to reduce hydrocarbons emitted into the atmosphere from the fuel
system. This reduction of hydrocarbons is accomplished by activated charcoals in the EVAP canister.
The fuel vapor in the sealed fuel tank is led into the EVAP canister which contains activated carbon and the
vapor is stored there when the engine is not operating 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 control 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.
PBIB1631E

EVAPORATIVE EMISSION SYSTEM
EC-637
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EVAP SERVICE PORT
Positive pressure is delivered to the EVAP system through the EVAP
service port. If fuel vapor leakage in the EVAP system occurs, use a
leak detector to locate the leak.
Removal and InstallationUBS00HE0
EVAP CANISTER
Tighten EVAP canister as shown in the figure.
EVAP CANISTER VENT CONTROL VALVE
1. Turn EVAP canister vent control valve counterclockwise.
2. Remove the EVAP canister vent control valve.
Always replace O-ring with a new one.
How to Detect Fuel Vapor LeakageUBS00HE1
CAUTION:

Do not use compressed air or a high pressure pump.

Do not exceed 4.12 kPa (0.042 kg/cm2 , 0.6 psi) of pressure in EVAP system.
NOTE:

Do not start engine.

Improper installation of EVAP service port adapter to the EVAP service port may cause a leak.
SEF 4 62 UA
BBIA0349E
BBIA0350E

AUTOMATIC SPEED CONTROL DEVICE (ASCD)
EC-647
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)PFP:18930
System DescriptionUBS00HE7
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 driver to keep vehicle at predetermined constant speed
without pressing 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 throttle control actuator to regulate engine speed.
Operation status of ASCD is indicated by CRUISE indicator and SET indicator in combination meter. If any
malfunction occurs in ASCD system, it automatically deactivates control.
SET OPERATION
Press ON/OFF(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 COAST/SET switch. (Then SET indicator in combination meter illuminates.)
ACCEL OPERATION
If the ACCEL/RESUME switch is pressed during cruise control driving, increase the vehicle speed until the
switch is released or vehicle speed reaches 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/TCS 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 the normal operating temperature, CRUISE lamp may
blink slowly.
When the engine coolant temperature decreases to the normal operating temperature, CRUISE lamp will
stop blinking and the cruise operation will be able to work by pressing COAST/SET switch or ACCEL/
RESUME switch.

Malfunction for some self-diagnoses regarding ASCD control: SET lamp will blink quickly.
If ON/OFF(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 COAST/SET 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.
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
Park/Neutral position (PNP)
switchGear position
Combination meter* Vehicle speed
TCM* Powertrain revolution

GI-1
GENERAL INFORMATION
A GENERAL INFORMATION
CONTENTS
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SECTION GI
Revision: August 20072004 QX56 PRECAUTIONS .......................................................... 3
Description ............................................................... 3
Precautions for Supplemental Restraint System
(SRS) “AIR BAG” and “SEAT BELT PRE-TEN-
SIONER” .................................................................. 3
Precautions for NVIS/IVIS (NISSAN/INFINITI
VEHICLE IMMOBILIZER SYSTEM - NATS) (If
Equipped) ................................................................. 3
General Precautions ................................................ 4
Precautions for Three Way Catalyst ......................... 5
Precautions for Fuel (Unleaded Premium Gasoline
Required) ................................................................. 5
Precautions for Multiport Fuel Injection System or
Engine Control System ............................................ 6
Precautions for Hoses .............................................. 6
HOSE REMOVAL AND INSTALLATION ............... 6
HOSE CLAMPING ................................................ 6
Precautions for Engine Oils ...................................... 7
HEALTH PROTECTION PRECAUTIONS ............. 7
Precautions for Air Conditioning ............................... 7
HOW TO USE THIS MANUAL ................................... 8
Description ............................................................... 8
Terms ....................................................................... 8
Units ......................................................................... 8
Contents ................................................................... 8
Relation between Illustrations and Descriptions ...... 9
Components ........................................................... 10
SYMBOLS ........................................................... 10
How to Follow Trouble Diagnoses ...........................11
DESCRIPTION .....................................................11
HOW TO FOLLOW TEST GROUPS IN TROU-
BLE DIAGNOSES ................................................11
HARNESS WIRE COLOR AND CONNECTOR
NUMBER INDICATION ....................................... 12
KEY TO SYMBOLS SIGNIFYING MEASURE-
MENTS OR PROCEDURES ............................... 13
How to Read Wiring Diagrams ............................... 15
CONNECTOR SYMBOLS ................................... 15
SAMPLE/WIRING DIAGRAM - EXAMPL - ......... 16DESCRIPTION .................................................... 17
Abbreviations .......................................................... 22
SERVICE INFORMATION FOR ELECTRICAL INCI-
DENT ......................................................................... 24
How to Check Terminal ........................................... 24
CONNECTOR AND TERMINAL PIN KIT ............ 24
HOW TO PROBE CONNECTORS ...................... 24
How to Perform Efficient Diagnosis for an Electrical
Incident ................................................................... 27
WORK FLOW ...................................................... 27
INCIDENT SIMULATION TESTS ........................ 27
CIRCUIT INSPECTION ....................................... 30
Control Units and Electrical Parts ........................... 35
PRECAUTIONS .................................................. 35
SMJ INSTALLATION ........................................... 36
CONSULT-II CHECKING SYSTEM .......................... 37
Description .............................................................. 37
Function and System Application ........................... 37
Nickel Metal Hydride Battery Replacement ............ 38
Checking Equipment .............................................. 38
CONSULT-II Start Procedure .................................. 38
CONSULT-II Data Link Connector (DLC) Circuit .... 39
INSPECTION PROCEDURE .............................. 39
LIFTING POINT ......................................................... 40
Pantograph Jack ..................................................... 40
Garage Jack and Safety Stand ............................... 40
2-Pole Lift ............................................................... 41
TOW TRUCK TOWING ............................................. 42
Tow Truck Towing ................................................... 42
2WD MODELS .................................................... 42
4WD MODELS .................................................... 43
Vehicle Recovery (Freeing a stuck vehicle) ............ 43
TIGHTENING TORQUE OF STANDARD BOLTS .... 44
Tightening Torque Table ......................................... 44
RECOMMENDED CHEMICAL PRODUCTS AND
SEALANTS ............................................................... 45
Recommended Chemical Products and Sealants ... 45
IDENTIFICATION INFORMATION ............................ 46
Model Variation ....................................................... 46
Identification Number .............................................. 47

PRECAUTIONS
GI-5
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Use approved bonding agent, sealants or their equivalents when required.

Use hand tools, power tools (disassembly only) and recom-
mended special tools where specified for safe and efficient ser-
vice repairs.

When repairing the fuel, oil, water, vacuum or exhaust systems,
check all affected lines for leaks.

Before servicing the vehicle:
Protect fenders, upholstery and carpeting with appropriate cov-
ers.
Take caution that keys, buckles or buttons do not scratch paint.
WA RN ING:
To prevent ECM from storing the diagnostic trouble codes, do not carelessly disconnect the harness
connectors which are related to the engine control system and TCM (transmission control module)
system. The connectors should be disconnected only when working according to the WORK FLOW of
TROUBLE DIAGNOSES in EC and AT sections.
Precautions for Three Way CatalystEAS00149
If a large amount of unburned fuel flows into the catalyst, the catalyst temperature will be excessively high. To
prevent this, follow the instructions.

Use unleaded gasoline only. Leaded gasoline will seriously damage the three way catalyst.

When checking for ignition spark or measuring engine compression, make tests quickly and only when
necessary.

Do not run engine when the fuel tank level is low, otherwise the engine may misfire, causing damage to
the catalyst.
Do not place the vehicle on flammable material. Keep flammable material off the exhaust pipe and the three
way catalyst.
Precautions for Fuel (Unleaded Premium Gasoline Required)EAS001KH
Use unleaded premium gasoline with an octane rating of at least 91 AKI (Anti-Knock Index) number (Research
octane number 96).
If unleaded premium gasoline is not available, unleaded regular gasoline with an octane rating of at least 87
AKI number (Research octane number 91) can be used, but only under the following precautions:

have the fuel tank filled only partially with unleaded regular gasoline, and fill up with unleaded premium
gasoline as soon as possible.

avoid full throttle driving and abrupt acceleration.
However, for maximum vehicle performance, the use of unleaded premium gasoline is recommended.
CAUTION:
Do not use leaded gasoline. Using leaded gasoline will damage the three way catalyst. Do not use E-85
fuel (85% fuel ethanol, 15% unleaded gasoline) unless the vehicle is specifically designed for E-85 fuel
PBIC0190E
SGI234