Vacuum cut INFINITI QX4 2001 Factory Owner's Guide

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

RESULTSº. If ªNGº is displayed, refer to ªDiagnostic
Procedureº, EC-595.
SEF530Q
Overall Function CheckNBEC0358Use this procedure to check the overall function of vacuum cut
valve bypass valve. During this check, the 1st trip DTC might not
be confirmed.
WITH GSTNBEC0358S011) Remove vacuum cut valve and vacuum cut valve bypass valve
as an assembly.
2) Apply vacuum to portAand check that there is no suction from
portB.
3) Apply vacuum to portBand check that there is suction from
portA.
4) Blow air in portBand check that there is a resistance to flow
out of portA.
5) Supply battery voltage to the terminal.
6) Blow air in portAand check that air flows freely out of portB.
7) Blow air in portBand check that air flows freely out of portA.
8) If NG, go to ªDiagnostic Procedureº, EC-595.
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DTC P1491 VACUUM CUT VALVE BYPASS VALVE
DTC Confirmation Procedure (Cont'd)
EC-593

Wiring DiagramNBEC0359
MEC972C
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Wiring Diagram
EC-594

Diagnostic ProcedureNBEC0360
1 INSPECTION START
Do you have CONSULT-II?
YesorNo
Ye s©GO TO 2.
No©GO TO 3.
2 CHECK VACUUM CUT VALVE BYPASS VALVE OPERATION
With CONSULT-II
1. Turn ignition switch ªOFFº.
2. Remove vacuum cut valve and vacuum cut valve bypass valve as an assembly.
3. Apply vacuum to port A and check that there is no suction from port B.
4. Apply vacuum to port B and check that there is suction from port A.
5. Blow air in port B and check that there is a resistance to flow out of port A.
6. Turn ignition switch ªONº.
7. Select ªVC/V BYPASS/Vº in ªACTIVE TESTº mode with CONSULT-II and touch ªONº.
8. Blow air in port A and check that air flows freely out of port B.
9. Blow air in port B and check that air flows freely out of port A.
SEF017Z
OK or NG
OK©GO TO 4.
NG©GO TO 5.
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DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure
EC-595

3 CHECK VACUUM CUT VALVE BYPASS VALVE OPERATION
Without CONSULT-II
1. Turn ignition switch ªOFFº.
2. Remove vacuum cut valve and vacuum cut valve bypass valve as an assembly.
3. Apply vacuum to port A and check that there is no suction from port B.
4. Apply vacuum to port B and check that there is suction from port A.
5. Blow air in port B and check that there is a resistance to flow out of port A.
6. Disconnect vacuum cut valve bypass valve harness connector.
7. Supply battery voltage to the terminal.
8. Blow air in port A and check that air flows freely out of port B.
9. Blow air in port B and check that air flows freely out of port A.
SEF914U
OK or NG
OK©GO TO 4.
NG©GO TO 7.
4 CHECK EVAP PURGE LINE
Check EVAP purge line between EVAP canister and fuel tank for clogging or disconnection.
OK or NG
OK©GO TO 5.
NG©Repair it.
5 CHECK EVAP PURGE PORT
Check EVAP purge port of fuel tank for clogging.
OK or NG
OK©GO TO 6.
NG©Clean EVAP purge port.
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-596

6 CHECK EVAP CANISTER
1. Pinch the fresh air hose.
2. Blow air into portAand check that it flows freely out of portB.
AEC630A
OK or NG
OK©GO TO 12.
NG©Replace EVAP canister.
7 CHECK BYPASS HOSE
Check bypass hoses for clogging.
OK or NG
OK©GO TO 8.
NG©Repair or replace hoses.
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DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-597

8 CHECK VACUUM CUT VALVE BYPASS VALVE
With CONSULT-II
1. Perform ªVC/V BYPASS/Vº in ªACTIVE TESTº mode.
2. Check air passage continuity and operation delay time under the following conditions.
SEF016Z
Without CONSULT-II
Check air passage continuity and operation delay time under the following conditions.
SEF358X
OK or NG
OK©GO TO 9.
NG©Replace vacuum cut valve bypass valve.
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-598

9 CHECK VACUUM CUT VALVE
Check vacuum cut valve as follows:
SEF379Q
a. Plug portCandDwith fingers.
b. Apply vacuum to portAand check that there is no suction from portB.
c. Apply vacuum to portBand check that there is suction from portA.
d. Blow air in portBand check that there is a resistance to flow out of portA.
e. Open portCandD.
f. Blow air in portAcheck that air flows freely out of portC.
g. Blow air in portBcheck that air flows freely out of portD.
OK or NG
OK©GO TO 10.
NG©Replace vacuum cut valve.
10 CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR HOSE
1. Turn ignition switch ªOFFº.
2. Check disconnection or improper connection of hose connected to EVAP control system pressure sensor.
OK or NG
OK©GO TO 11.
NG©Repair or replace.
11 CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR CONNECTOR
1. Disconnect EVAP control system pressure sensor harness connector.
SEF495R
2. Check connectors for water.
Water should not exist.
OK or NG
OK©GO TO 12.
NG©Replace EVAP control system pressure sensor.
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DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-599

12 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 0.5 m
(19.7 in) onto a hard surface such as a concrete floor; use a new one.
OK or NG
OK©GO TO 13.
NG©Replace EVAP control system pressure sensor.
13 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 14.
NG©Clean the rubber tube using an air blower.
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-600

14 CHECK EVAP CANISTER VENT CONTROL VALVE-I
1. Remove EVAP canister vent control valve from EVAP canister.
2. Check portionBof EVAP canister vent control valve for being rusted.
SEF337X
OK or NG
OK©GO TO 15.
NG©Replace EVAP canister vent control valve.
15 CHECK EVAP CANISTER VENT CONTROL VALVE-II
With CONSULT-II
1. Reconnect harness disconnected connectors.
2. Turn ignition switch ON.
3. Perform ªVENT CONTROL/Vº in ªACTIVE TESTº mode.
4. Check air passage continuity and operation delay time.
SEF991Y
Without CONSULT-II
Check air passage continuity and operation delay time under the following conditions.
SEF339X
Make sure new O-ring is installed properly.
OK or NG
OK©GO TO 17.
NG©GO TO 16.
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DTC P1491 VACUUM CUT VALVE BYPASS VALVE
Diagnostic Procedure (Cont'd)
EC-601