2001 INFINITI QX4 fuel pressure

IEVAP purge line rubber tube bent.
IBlocked or bent rubber tube to EVAP control system pressure
sensor
ILoose or disconnected rubber tube
IEVAP canister vent control valve and the circuit
IEVAP canister purge volume control solenoid valve
IAbsolute pressure sensor
IFuel tank temperature sensor
IO-ring of EVAP canister vent control valve is missing or dam-
aged.
IWater separator
IEVAP canister is saturated with water.
IFuel level sensor and the circuit
IEVAP control system pressure sensor
SEF881X
SEF882X
SEF883X
DTC Confirmation ProcedureNBEC0317CAUTION:
Never remove fuel filler cap during the DTC confirmation pro-
cedure.
NOTE:
IIf DTC P1441 is displayed with P0440, perform TROUBLE
DIAGNOSIS FOR DTC P1441 first.
IIf ªDIAGNOSTIC TROUBLE CODE CONFIRMATION PRO-
CEDUREº has been previously conducted, always turn
ignition switch ªOFFº and wait at least 5 seconds before
conducting the next test.
IAfter repair, make sure that the hoses and clips are
installed properly.
TESTING CONDITION:
IOpen engine hood before conducting following proce-
dure.
IIf any of following condition is met just before the DTC
confirmation procedure, leave the vehicle for more than 1
hour.
a)Fuel filler cap is removed.
b)Refilled or drained the fuel.
c)EVAP component parts is/are removed.
IBefore performing the following procedure, confirm that
battery voltage is more than 11V at idle.
With CONSULT-II
1) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT-II.
2) Make sure the following conditions are met.
FUEL LEVEL SE: 1.08 - 0.2V
COOLAN TEMP/S: 0 - 32ÉC (32 - 90ÉF)
FUEL T/TMP SE: 0 - 35ÉC (32 - 95ÉF)
INT A/TEMP SE: More than 0ÉC (32ÉF)
If NG, turn ignition switch ªOFFº and leave the vehicle in a cool
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DTC P1441 EVAP CONTROL SYSTEM (VERY SMALL LEAK)
Possible Cause (Cont'd)
EC-527

place or refilling/draining fuel until the output voltage condition
of the ªFUEL LEVEL SEº meets within the range above and
leave the vehicle for more than 1 hour. Then start from step 1).
3) Turn ignition switch ªOFFº and wait at least 5 seconds.
4) Turn ignition switch ªONº.
5) Select ªEVAP VERY/SML LEAK P1441º of ªEVAPORATIVE
SYSTEMº in ªDTC WORK SUPPORTº mode with CONSULT-
II.
Follow the instruction displayed.
6) Make sure that ªOKº is displayed.
If ªNGº is displayed, refer to ªDiagnostic Procedureº, EC-529.
NOTE:
IIf the engine speed cannot be maintained within the range
displayed on CONSULT-II screen, go to ªBasic
inspectionº, EC-101.
IMake sure that EVAP hoses are connected to EVAP canis-
ter purge volume control solenoid valve properly.
OVERALL FUNCTION CHECKNBEC0317S05With GST
Use this procedure to check the overall function of the EVAP very
small leak function. During this check, a 1st trip DTC might not be
confirmed.
SEF462UA
CAUTION:
INever use compressed air, doing so may damage the
EVAP system.
IDo not start engine.
IDo not exceeded 4.12 kPa (0.042 kg/cm
2, 0.6 psi).
1) Attach the EVAP service port adapter securely to the EVAP
service port.
2) Set the pressure pump and a hose.
3) Also set a vacuum gauge via 3-way connector and a hose.
4) Turn ignition switch ªONº.
5) Connect GST and select mode 8.
6) Using mode 8 control the EVAP canister vent control valve
(close) and vacuum cut valve bypass valve (open).
7) Apply pressure and make sure the following conditions are
satisfied.
Pressure to be applied: 2.7 kPa (20 mmHg, 0.79 inHg)
Time to be waited after the pressure drawn in to the EVAP
system and the pressure to be dropped: 60 seconds and
the pressure should not be dropped more than 0.4 kPa (3
mmHg, 0.12 inHg)
If NG, go to diagnostic procedure, EC-529.
NOTE:
For more information, refer to GST instruction manual.
DTC P1441 EVAP CONTROL SYSTEM (VERY SMALL LEAK)
DTC Confirmation Procedure (Cont'd)
EC-528

4 CHECK FUEL TANK VACUUM RELIEF VALVE
1. Wipe clean valve housing.
2. Check valve opening pressure and vacuum.
SEF427N
SEF943S
Pressure:
15.3 - 20.0 kPa (0.156 - 0.204 kg/cm2, 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)
CAUTION:
Use only a genuine fuel filler cap as a replacement. If an incorrect fuel filler cap is used, the MIL may come on.
OK or NG
OK©GO TO 5.
NG©Replace fuel filler cap with a genuine one.
DTC P1441 EVAP CONTROL SYSTEM (VERY SMALL LEAK)
Diagnostic Procedure (Cont'd)
EC-530

18 CHECK ABSOLUTE PRESSURE SENSOR
1. Remove absolute pressure sensor with its harness connector connected.
SEF961Y
2. Remove hose from absolute pressure sensor.
3. Install a vacuum pump to absolute pressure sensor.
4. Turn ignition switch ªONº and check output voltage between ECM terminal 80 and engine ground under the following
conditions.
SEF300XA
CAUTION:
IAlways calibrate the vacuum pump gauge when using it.
IDo not apply below þ93.3 kPa (±700 mmHg, ±27.56 inHg) or over 101.3 kPa (760 mmHg, 29.92 inHg) of pressure.
OK or NG
OK©GO TO 19.
NG©Replace absolute pressure sensor.
19 CHECK FUEL TANK TEMPERATURE SENSOR
1. Remove fuel level sensor unit.
2. Check resistance between fuel level sensor unit and fuel pump terminals 1 and 2 by heating with hot water or heat gun
as shown in the figure.
SEF974Y
OK or NG
OK©GO TO 20.
NG©Replace fuel level sensor unit.
DTC P1441 EVAP CONTROL SYSTEM (VERY SMALL LEAK)
Diagnostic Procedure (Cont'd)
EC-538

20 CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR
1. Remove EVAP control system pressure sensor with its harness connector connected.
CAUTION:
INever apply force to the air hole protector of the sensor if equipped.
SEF799W
2. Remove hose from EVAP control system pressure sensor.
3. Turn ignition switch ªONº.
4. Use pump to apply vacuum and pressure to EVAP control system pressure sensor as shown in figure.
CAUTION:
IAlways calibrate the vacuum pump gauge when using it.
IDo not apply below þ20 kPa (þ150 mmHg, þ5.91 inHg) or over 20 kPa (150 mmHg, 5.91 inHg) of pressure.
5. Check input voltage between ECM terminal 84 and ground.
SEF342X
CAUTION:
IDiscard and EVAP control system pressure sensor which has been dropped from a height of more than 0.5m
(19.7in) onto a hard surface such as a concrete floor; use a new one.
OK or NG
OK©GO TO 21.
NG©Replace EVAP control system pressure sensor.
21 CHECK EVAP PURGE LINE
Check EVAP purge line (pipe, rubber tube, fuel tank and EVAP canister) for cracks or improper connection.
Refer to ªEvaporative Emission Systemº, EC-32.
OK or NG
OK©GO TO 22.
NG©Repair or reconnect the hose.
22 CLEAN EVAP PURGE LINE
Clean EVAP purge line (pipe and rubber tube) using air blower.
©GO TO 23.
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DTC P1441 EVAP CONTROL SYSTEM (VERY SMALL LEAK)
Diagnostic Procedure (Cont'd)
EC-539

Possible CauseNBEC0591IEVAP canister vent control valve
IEVAP control system pressure sensor and circuit
IBlocked rubber tube to EVAP canister vent control valve
IWater separator
IEVAP canister is saturated with water.
IVacuum cut valve
DTC Confirmation ProcedureNBEC0342NOTE:
IIf DTC P1448 is displayed with P0440 or P1440, perform
trouble diagnosis for DTC P1448 first.
IIf ªDTC Confirmation Procedureº has been previously
conducted, always turn ignition switch ªOFFº and wait at least
10 seconds before conducting the next test.
SEF565X
SEF566X
SEF567X
WITH CONSULT-IINBEC0342S01TESTING CONDITION:
IPerform ªDTC WORK SUPPORTº when the fuel level is
between 1/4 to 3/4 full and vehicle is placed on flat level
surface.
IOpen engine hood before conducting the following proce-
dure.
1) Turn ignition switch ªONº.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT-II.
4) Make sure that the following conditions are met.
COOLAN TEMP/S 0 - 70ÉC (32 - 158ÉF)
INT/A TEMP SE 0 - 30ÉC (32 - 86ÉF)
5) Select ªEVAP SML LEAK P0440/P1440º of ªEVAPORATIVE
SYSTEMº in ªDTC WORK SUPPORTº mode with CONSULT-
II.
Follow the instruction displayed.
NOTE:
If the engine speed cannot be maintained within the range
displayed on the CONSULT-II screen, go to ªBasic Inspectionº,
EC-101.
6) Make sure that ªOKº is displayed.
If ªNGº is displayed, go to the following step.
NOTE:
Make sure that EVAP hoses are connected to EVAP canister
purge volume control solenoid valve properly.
7) Stop engine and wait at least 10 seconds, then turn ªONº.
8) Disconnect hose from water separator.
9) Select ªVENT CONTROL/Vº of ªACTIVE TESTº mode with
CONSULT-II.
10) Touch ªONº and ªOFFº alternately.
DTC P1448 EVAPORATIVE EMISSION (EVAP) CANISTER VENT CONTROL
VALVE (OPEN)
Possible Cause
EC-574

On Board Diagnosis LogicNBEC0356Malfunction is detected when vacuum cut valve bypass valve does
not operate properly.
Possible CauseNBEC0593IVacuum cut valve bypass valve
IVacuum cut valve
IBypass hoses for clogging
IEVAP control system pressure sensor and circuit
IEVAP canister vent control valve
IHose between fuel tank and vacuum cut valve clogged
IHose between vacuum cut valve and EVAP canister clogged
IEVAP canister
IEVAP purge port of fuel tank for clogging
SEF210Y
SEF211Y
SEF239Y
DTC Confirmation ProcedureNBEC0357CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
TESTING CONDITION:
For best results, perform test at a temperature of 5 to 30ÉC (41
to 86ÉF).
WITH CONSULT-IINBEC0357S011) Turn ignition switch ªONº.
2) Start engine and warm it up to normal operating temperature.
3) Turn ignition switch ªOFFº and wait at least 10 seconds.
4) Start engine and let it idle for at least 70 seconds.
5) Select ªVC CUT/V BP/V P1491º of ªEVAPORATIVE SYSTEMº
in ªDTC WORK SUPPORTº mode with CONSULT-II.
6) Touch ªSTARTº.
7) When the following conditions are met, ªTESTINGº will be dis-
played on the CONSULT-II screen. Maintain the conditions
continuously until ªTESTINGº changes to ªCOMPLETEDº. (It
will take at least 30 seconds.)
ENG SPEED Idle speed or more
Selector lever Suitable position
Vehicle speed 37 km/h (23 MPH) or more
B/FUEL SCHDL 1.3 - 10 msec
If ªTESTINGº is not displayed after 5 minutes, retry from
step 3.
8) Make sure that ªOKº is displayed after touching ªSELF-DIAG
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
On Board Diagnosis Logic
EC-592

Diagnostic ProcedureNBEC0397
1 CHECK OVERALL FUNCTION
1. Turn ignition switch ªONº.
2. Pinch fuel feed hose with two fingers.
SEF025Z
Fuel pressure pulsation should be felt on the fuel feed hose for 1 second after ignition switch is turned ªONº.
OK or NG
OK©INSPECTION END
NG©GO TO 2.
2 CHECK FUEL PUMP RELAY-1 and -2 POWER SUPPLY CIRCUIT-I
1. Turn ignition switch ªOFFº.
2. Disconnect fuel pump relay-1 and -2.
SEF346Z
3. Turn ignition switch ªONº.
4. Check voltage between terminals 2 and ground with CONSULT-II or tester.
SEF347Z
OK or NG
OK©GO TO 4.
NG©GO TO 3.
FUEL PUMP
Diagnostic Procedure
EC-628