2001 INFINITI QX4 Engine control

IWhen the engine coolant temperature becomes excessively high.
IWhen operating power steering during low engine speed or low vehicle speed.
IWhen engine speed is excessively low.
IWhen refrigerant pressure is excessively low or high.
Fuel Cut Control (at no load & high engine
speed)
DESCRIPTIONNBEC0017Input/Output Signal ChartNBEC0017S01
Sensor Input Signal to ECMECM func-
tionActuator
Vehicle speed sensor Vehicle speed
Fuel cut
controlInjectors Park/neutral position (PNP) switch Neutral position
Throttle position sensor Throttle position
Engine coolant temperature sensor Engine coolant temperature
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
If the engine speed is above 1,800 rpm with no load (for example, in neutral and engine speed over 1,800
rpm) fuel will be cut off after some time. The exact time when the fuel is cut off varies based on engine speed.
Fuel cut will operate until the engine speed reaches 1,500 rpm, then fuel cut is cancelled.
NOTE:
This function is different from deceleration control listed under ªMultiport Fuel Injection (MFI) Systemº, EC-28.
Evaporative Emission System
DESCRIPTIONNBEC0018
SEF927U
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
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Air Conditioning Cut Control (Cont'd)
EC-32

operates, the flow rate of vapor controlled by EVAP canister purge volume control solenoid valve is propor-
tionally regulated as the air flow increases.
EVAP canister purge volume control solenoid valve also shuts off the vapor purge line during decelerating and
idling.
SEF428T
INSPECTIONNBEC0019EVAP CanisterNBEC0019S01Check EVAP canister as follows:
1. Pinch the fresh air hose.
2. Blow air into portAand check that it flows freely out of portB.
SEF231SB
Tightening TorqueNBEC0019S02Tighten EVAP canister as shown in the figure.
Make sure new O-ring is installed properly between EVAP can-
ister and EVAP canister vent control valve.
SEF427N
SEF943S
Fuel Tank Vacuum Relief Valve (Built into fuel filler cap)NBEC0019S031. Wipe clean valve housing.
2. Check valve opening pressure and vacuum.
Pressure:
15.3 - 20.0 kPa (0.156 - 0.204 kg/cm
2, 2.22 - 2.90 psi)
Vacuum:
þ6.0 to þ3.3 kPa (þ0.061 to þ0.034 kg/cm
2, þ0.87 to
þ0.48 psi)
3. If out of specification, replace fuel filler cap as an assembly.
CAUTION:
Use only a genuine fuel filler cap as a replacement. If an incor-
rect fuel filler cap is used, the MIL may come on.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-33

Vacuum Cut Valve and Vacuum Cut Valve Bypass ValveNBEC0019S04Refer to EC-591.
Evaporative Emission (EVAP) Canister Purge Volume
Control Solenoid Valve
NBEC0019S05Refer to EC-367.
Fuel Tank Temperature SensorNBEC0019S06Refer to EC-309.
SEF462UA
Evap Service PortNBEC0019S07Positive 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.
SEF200U
PEF838U
PEF917U
How to Detect Fuel Vapor LeakageNBEC0019S08CAUTION:
INever use compressed air or a high pressure pump.
IDo not exceed 4.12 kPa (0.042 kg/cm
2, 0.6 psi) of pressure
in EVAP system.
NOTE:
IDo not start engine.
IImproper installation of EVAP service port adapter to the EVAP
service port may cause a leak.
With CONSULT-IINBEC0019S08011) Attach the EVAP service port adapter securely to the EVAP
service port.
2) Also attach the pressure pump and hose to the EVAP service
port adapter.
3) Turn ignition switch ªONº.
4) Select the ªEVAP SYSTEM CLOSEº of ªWORK SUPPORT
MODEº with CONSULT-II.
5) Touch ªSTARTº. A bar graph (Pressure indicating display) will
appear on the screen.
6) Apply positive pressure to the EVAP system until the pressure
indicator reaches the middle of the bar graph.
7) Remove EVAP service port adapter and hose with pressure
pump.
8) Locate the leak using a leak detector. Refer to ªEVAPORATIVE
EMISSION LINE DRAWINGº, EC-36.
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-34

SEF462UA
SEF598U
Without CONSULT-IINBEC0019S08021) Attach the EVAP service port adapter securely to the EVAP
service port.
2) Also attach the pressure pump with pressure gauge to the
EVAP service port adapter.
3) Apply battery voltage to between the terminals of both EVAP
canister vent control valve and vacuum cut valve bypass valve
to make a closed EVAP system.
4) To locate the leak, deliver positive pressure to the EVAP sys-
tem until pressure gauge points reach 1.38 to 2.76 kPa (0.014
to 0.028 kg/cm
2, 0.2 to 0.4 psi).
5) Remove EVAP service port adapter and hose with pressure
pump.
6) Locate the leak using a leak detector. Refer to ªEVAPORATIVE
EMISSION LINE DRAWINGº, EC-36.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-35

EVAPORATIVE EMISSION LINE DRAWINGNBEC0020
SEF932Y
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-36

SEF870T
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-37

SEF372Q
SEF559A
Positive Crankcase Ventilation
DESCRIPTIONNBEC0021This system returns blow-by gas to the intake manifold.
The positive crankcase ventilation (PCV) valve is provided to con-
duct crankcase blow-by gas to the intake manifold.
During partial throttle operation of the engine, the intake manifold
sucks the blow-by gas through the PCV valve.
Normally, the capacity of the valve is sufficient to handle any
blow-by and a small amount of ventilating air.
The ventilating air is then drawn from the air inlet tubes into the
crankcase. In this process the air passes through the hose con-
necting air inlet tubes to rocker cover.
Under full-throttle condition, the manifold vacuum is insufficient to
draw the blow-by flow through the valve. The flow goes through the
hose connection in the reverse direction.
On vehicles with an excessively high blow-by, the valve does not
meet the requirement. This is because some of the flow will go
through the hose connection to the air inlet tubes under all
conditions.
SEC137A
INSPECTIONNBEC0022PCV (Positive Crankcase Ventilation) ValveNBEC0022S01With engine running at idle, remove PCV valve ventilation hose
from PCV valve; if the valve is working properly, a hissing noise will
be heard as air passes through it and a strong vacuum should be
felt immediately when a finger is placed over valve inlet.
ET277
PCV Valve Ventilation HoseNBEC0022S021. Check hoses and hose connections for leaks.
2. Disconnect all hoses and clean with compressed air. If any
hose cannot be freed of obstructions, replace.
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Positive Crankcase Ventilation
EC-38

18 ERASE UNNECESSARY DTC
After this inspection, unnecessary DTC No. might be displayed.
Erase the stored memory in ECM and TCM (Transmission control module).
Refer to ªHOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATIONº, EC-72 and AT-35, ªHOW TO ERASE
DTCº.
With CONSULT-II©GO TO 19.
Without CONSULT-II©GO TO 20.
19 CHECK HEATED OXYGEN SENSOR 1 (FRONT) (BANK 2) SIGNAL
With CONSULT-II
1. Run engine at about 2,000 rpm for about 2 minutes under no-load.
2. See ªHO2S1 MNTR (B2)º in ªDATA MONITORº mode.
3. Running engine at 2,000 rpm under no-load (engine is warmed up to normal operating temperature.), check that the
monitor fluctuates between ªLEANº and ªRICHº more than 5 times during 10 seconds.
SEF945Y
OK or NG
OK©GO TO 23.
NG (Monitor does not
fluctuate.)©GO TO 28.
NG (Monitor fluctuates
less than 5 times.)©GO TO 21.
20 CHECK HEATED OXYGEN SENSOR 1 (FRONT) (BANK 2) SIGNAL
Without CONSULT-II
1. Run engine at about 2,000 rpm for about 2 minutes under no-load.
2. Set voltmeter probe between ECM terminal 62 and ground.
3. Make sure that the voltage fluctuates between 0 - 0.3V and 0.6 - 1.0V more than 5 times during 10 seconds at 2,000
rpm.
1 time: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V
2 times: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V®0.6 - 1.0V®0 - 0.3V
OK or NG
OK©GO TO 23.
NG (Voltage does not
fluctuate.)©GO TO 28.
NG (Voltage fluctuates
less than 5 times.)©GO TO 21.
BASIC SERVICE PROCEDURE
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (Cont'd)
EC-50