2001 INFINITI QX4 air conditioner

System ChartNBEC0013
Input (Sensor) ECM Function Output (Actuator)
ICamshaft position sensor (PHASE)
ICrankshaft position sensor (REF)
IMass air flow sensor
IEngine coolant temperature sensor
IHeated oxygen sensor 1 (front)
IIgnition switch
IThrottle position sensor
IClosed throttle position switch*3
IPark/neutral position (PNP) switch
IAir conditioner switch
IKnock sensor
IIntake air temperature sensor
IAbsolute pressure sensor
IEVAP control system pressure sensor*1
IBattery voltage
IPower steering oil pressure switch
IVehicle speed sensor
IFuel tank temperature sensor*1
ICrankshaft position sensor (POS)
IHeated oxygen sensor 2 (rear)*2
ITCM (Transmission control module)
IRefrigerant pressure sensor
IElectrical load
IFuel level sensor*1Fuel injection & mixture ratio control Injectors
Electronic ignition system Power transistor
Idle air control system IACV-AAC valve
Fuel pump control Fuel pump relay
On board diagnostic system MIL (On the instrument panel)
Swirl control valve controlSwirl control valve control solenoid
valve
Power valve control VIAS control solenoid valve
Heated oxygen sensor 1 heater (front) con-
trolHeated oxygen sensor 1 heater
(front)
Heated oxygen sensor 2 heater (rear) controlHeated oxygen sensor 2 heater
(rear)
EVAP canister purge flow controlEVAP canister purge volume con-
trol solenoid valve
Air conditioning cut control Air conditioner relay
ON BOARD DIAGNOSIS for EVAP systemIEVAP canister vent control valve
IVacuum cut valve bypass valve
*1: These sensors are not used to control the engine system. They are used only for the on board diagnosis.
*2: This sensor is not used to control the engine system under normal conditions.
*3: This switch will operate in place of the throttle position sensor to control EVAP parts if the sensor malfunctions.GI
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ENGINE AND EMISSION CONTROL OVERALL SYSTEM
System Chart
EC-27

Multiport Fuel Injection (MFI) System
DESCRIPTIONNBEC0014Input/Output Signal ChartNBEC0014S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed (POS signal)
Fuel injec-
tion & mix-
ture ratio
controlInjectors Crankshaft position sensor (REF) Engine speed (REF signal)
Camshaft position sensor (PHASE) Piston position
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Heated oxygen sensor 1 (front) Density of oxygen in exhaust gas
Throttle position sensorThrottle position
Throttle valve idle position
Park/neutral position (PNP) switch Gear position
Vehicle speed sensor Vehicle speed
Ignition switch Start signal
Air conditioner switch Air conditioner operation
Knock sensor Engine knocking condition
Battery Battery voltage
Absolute pressure sensor Ambient air barometric pressure
Power steering oil pressure switch Power steering operation
Heated oxygen sensor 2 (rear)* Density of oxygen in exhaust gas
*: Under normal conditions, this sensor is not for engine control operation.
Basic Multiport Fuel Injection SystemNBEC0014S02The 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). The 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 Increase/Decrease CompensationNBEC0014S03In addition, the amount of fuel injected is compensated to improve engine performance under various oper-
ating conditions as listed below.

IDuring warm-up
IWhen starting the engine
IDuring acceleration
IHot-engine operation
IWhen selector lever is changed from ªNº to ªDº
IHigh-load, high-speed operation

IDuring deceleration
IDuring high engine speed operation
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Multiport Fuel Injection (MFI) System
EC-28

System DescriptionNBEC0015S02
SEF742M
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of
the engine. The ignition timing data is stored in the ECM. This data forms the map shown.
The ECM receives information such as the injection pulse width and camshaft position sensor signal. Com-
puting this information, ignition signals are transmitted to the power transistor.
e.g., N: 1,800 rpm, Tp: 1.50 msec
A ÉBTDC
During the following conditions, the ignition timing is revised by the ECM according to the other data stored
in the ECM.
IAt starting
IDuring warm-up
IAt idle
IAt low battery voltage
IDuring acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.
Air Conditioning Cut Control
DESCRIPTIONNBEC0016Input/Output Signal ChartNBEC0016S01
Sensor Input Signal to ECM ECM function Actuator
Air conditioner switch Air conditioner ªONº signal
Air conditioner
cut controlAir conditioner relay Throttle position sensor Throttle valve opening angle
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Vehicle speed sensor Vehicle speed
Refrigerant pressure sensor Refrigerant pressure
Power steering oil pressure switch Power steering operation
System DescriptionNBEC0016S02This system improves engine operation when the air conditioner is used.
Under the following conditions, the air conditioner is turned off.
IWhen the accelerator pedal is fully depressed.
IWhen cranking the engine.
IAt high engine speeds.
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ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Electronic Ignition (EI) System (Cont'd)
EC-31

IAir intake system
(Oil filler cap, oil level gauge, etc.)
IFuel pressure
IEngine compression
IThrottle valve
IEvaporative emission system
2) On air conditioner equipped models, checks should be carried out while the air conditioner is ªOFFº.
3) On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio,
checks should be carried out while shift lever is in ªNº position.
4) When measuring ªCOº percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5) Turn off headlamps, heater blower, rear defogger.
6) Keep front wheels pointed straight ahead.
7) Make the check after the cooling fan has stopped.
BASIC SERVICE PROCEDURE
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (Cont'd)
EC-44

SEF452Y
Idle Air Volume LearningNBEC0642
SEF454Y
SEF455Y
DESCRIPTIONNBEC0642S01ªIdle Air Volume Learningº is an operation to learn the idle air vol-
ume that keeps each engine within the specific range. It must be
performed under any of the following conditions:
IEach time IACV-AAC valve, throttle body or ECM is replaced.
IIdle speed or ignition timing is out of specification.
PRE-CONDITIONINGNBEC0642S02Before performing ªIdle Air Volume Learningº, make sure that all of
the following conditions are satisfied.
Learning will be cancelled if any of the following conditions are
missed for even a moment.
IBattery voltage: More than 12.9V (At idle)
IEngine coolant temperature: 70 - 99ÉC (158 - 210ÉF)
IPNP switch: ON
IElectric load switch: OFF
(Air conditioner, headlamp, rear window defogger)
On vehicles equipped with daytime running light systems, if
the parking brake is applied before the engine is started the
headlamp will not illuminate.
ICooling fan motor: Not operating
ISteering wheel: Neutral (Straight-ahead position)
IVehicle speed: Stopped
ITransmission: Warmed-up
For A/T models with CONSULT-II, drive vehicle until ªFLUID
TEMP SEº in ªDATA MONITORº mode of ªA/Tº system indi-
cates less than 0.9V.
For A/T models without CONSULT-II, drive vehicle for 10 min-
utes.
OPERATION PROCEDURENBEC0642S03With CONSULT-IINBEC0642S03011. Turn ignition switch ªONº and wait at least 1 second.
2. Turn ignition switch ªOFFº and wait at least 10 seconds.
3. Start engine and warm it up to normal operating temperature.
4. Check that all items listed under the topic ªPRE-CONDITION-
INGº (previously mentioned) are in good order.
5. Turn ignition switch ªOFFº and wait at least 10 seconds.
6. Start the engine and let it idle for at least 30 seconds.
7. Select ªIDLE AIR VOL LEARNº in ªWORK SUPPORTº mode.
8. Touch ªSTARTº and wait 20 seconds.
9. Make sure that ªCMPLTº is displayed on CONSULT-II screen.
If ªINCMPº is displayed, ªIdle Air Volume Learningº will not be
carried out successfully. In this case, find the cause of the
problem by referring to the NOTE below.
10. Rev up the engine two or three times. Make sure that idle
speed and ignition timing are within specifications.
ITEM SPECIFICATION
Idle speed 750±50 rpm (in ªPº or ªNº position)
Ignition timing 15ɱ5É BTDC (in ªPº or ªNº position)
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BASIC SERVICE PROCEDURE
Idle Air Volume Learning
EC-57

ENGINE CONTROL COMPONENT PARTS/CONTROL
SYSTEMS APPLICATION
NBEC0034S02
ItemDIAGNOSTIC TEST MODE
WORK
SUP-
PORTSELF-DIAGNOSTIC
RESULTS
D ATA
MONI-
TORD ATA
MONI-
TOR
(SPEC)ACTIVE
TESTDTC & SRT
CONFIRMATION
DTC*1FREEZE
FRAME
DATA*2SRT
STATUSDTC
WORK
SUP-
PORT
ENGINE CONTROL COMPONENT PARTS
INPUT
Crankshaft position sensor
(POS)XXXX
Crankshaft position sensor (REF) X X X
Mass air flow sensor X X X
Engine coolant temperature sen-
sorXXXXX
Heated oxygen sensor 1 (front) X X X X X
Heated oxygen sensor 2 (rear) X X X X X
Vehicle speed sensorXXXX
Throttle position sensor X X X
Fuel tank temperature sensor X X X X
EVAP control system pressure
sensorXXX
Absolute pressure sensor X X X
Intake air temperature sensor X X X
Knock sensor X
Ignition switch (start signal) X X
Closed throttle position switch X X X
Closed throttle position switch
(throttle position sensor signal)XX
Air conditioner switch X X
Park/neutral position (PNP)
switchXXX
Power steering oil pressure
switchXX
Battery voltage X X
Ambient air temperature switch X X
Load signal X X
Swirl control valve control
vacuum check switchXXX
Fuel level sensor X X X
Intake valve timing control posi-
tion sensorXXX
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
CONSULT-II (Cont'd)
EC-82

ItemDIAGNOSTIC TEST MODE
WORK
SUP-
PORTSELF-DIAGNOSTIC
RESULTS
D ATA
MONI-
TORD ATA
MONI-
TOR
(SPEC)ACTIVE
TESTDTC & SRT
CONFIRMATION
DTC*1FREEZE
FRAME
DATA*2SRT
STATUSDTC
WORK
SUP-
PORT
ENGINE CONTROL COMPONENT PARTS
OUTPUT
Injectors X X X
Power transistor (Ignition timing)X
(Ignition
signal)XXX
IACV-AAC valve X X X X
EVAP canister purge volume
control solenoid valveX XXX X
Air conditioner relay X X
Fuel pump relay X X X X
Heated oxygen sensor 1 (front)
heaterXXXX
Heated oxygen sensor 2 (rear)
heaterXXXX
EVAP canister vent control valve X X X X
Vacuum cut valve bypass valve X X X X X
Swirl control valve control sole-
noid valveX XXX
VIAS control solenoid valve X X X
Intake valve timing control sole-
noid valveX XXX
Calculated load value X X X
X: Applicable
*1: This item includes 1st trip DTCs.
*2: This mode includes 1st trip freeze frame data or freeze frame data. The items appear on CONSULT-II screen in freeze frame data
mode only if a 1st trip DTC or DTC is detected. For details, refer to EC-60.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
CONSULT-II (Cont'd)
EC-83

Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
INT/A TEMP SE
[ÉC] or [ÉF]qqIThe intake air temperature determined
by the signal voltage of the intake air
temperature sensor is indicated.
EVAP SYS PRES [V]qIThe signal voltage of EVAP control sys-
tem pressure sensor is displayed.
ABSOL PRES/SE [V]qIThe signal voltage of the absolute pres-
sure sensor is displayed.
FUEL LEVEL SE [V]qIThe signal voltage of the fuel level sen-
sor is displayed.
START SIGNAL
[ON/OFF]qqIIndicates [ON/OFF] condition from the
starter signal.IAfter starting the engine, [OFF] is dis-
played regardless of the starter signal.
CLSD THL POS
[ON/OFF]qqIIndicates idle position [ON/OFF] com-
puted by ECM according to the throttle
position sensor signal.
CLSD THL/P SW
[ON/OFF]qIIndicates mechanical contact [ON/OFF]
condition of the closed throttle position
switch.
AIR COND SIG
[ON/OFF]qqIIndicates [ON/OFF] condition of the air
conditioner switch as determined by the
air conditioner signal.
P/N POSI SW
[ON/OFF]qqIIndicates [ON/OFF] condition from the
park/neutral position (PNP) switch sig-
nal.
PW/ST SIGNAL
[ON/OFF]qqI[ON/OFF] condition of the power steer-
ing oil pressure switch determined by
the power steering oil pressure signal is
indicated.
LOAD SIGNAL
[ON/OFF]qqIIndicates [ON/OFF] condition from the
electrical load signal and/or lighting
switch.
ON ... rear defogger is operating and/or
lighting switch is on.
OFF ... rear defogger is not operating
and lighting switch is not on.
IGNITION SW
[ON/OFF]qIIndicates [ON/OFF] condition from igni-
tion switch.
SWRL CONT S/V
[ON/OFF]qIThe control condition of the swirl con-
trol valve control solenoid valve (deter-
mined by ECM according to the input
signals) is indicated.
ION ... Swirl control valve is closed.
OFF ... Swirl control valve is opened.
INJ PULSE-B1
[msec]q
IIndicates the actual fuel injection pulse
width compensated by ECM according
to the input signals.IWhen the engine is stopped, a certain
computed value is indicated.
INJ PULSE-B2
[msec]
B/FUEL SCHDL
[msec]qIªBase fuel scheduleº indicates the fuel
injection pulse width programmed into
ECM, prior to any learned on board
correction.
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
CONSULT-II (Cont'd)
EC-88