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ase_master327
ase_master327, Shop owner
Category: Nissan
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Experience:  +15 years experience with Nissans. Bumper to bumper diagnosis & repair.
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2001 nissan altima gxe: the vacuum cut valve bypass valve what

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p1491 code coming up on a 2001 nissan altima gxe. It is stated as the "vacuum cut valve bypass valve" what are the steps to verify exactly what is the problem and what needs to be replaced?

Hello, and thank you for choosing Just Answer!

You are WISE for wanting to test before replacing. Laughing You really need a scantool for this one, though.

Here is everything Nissan has on the P1491 on your Altima.

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COMPONENT DESCRIPTION
The vacuum cut valve and vacuum cut valve bypass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister.

The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank.

The vacuum cut valve bypass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve bypass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then bypassed to apply intake manifold vacuum to the fuel tank.

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DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a safe speed.

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF " and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:

  • For best results, perform test at a temperature of 0 °C (32 °F) or more.
  • This test may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a road test is expected to be easier, it is unnecessary to lift the vehicle.

Before performing the following procedure, confirm that battery voltage is more than 11 V .

With Consult

  1. Turn ignition switch "ON ".
  2. Start engine and warm it up to normal operating temperature.
  3. Turn ignition switch "OFF " and wait at least 5 seconds .
  4. Start engine and let it idle for at least 1 minute .
  5. Select "VC CUT/V BP/V P1491" of "EVAPORATIVE SYSTEM" in "DTC WORK SUPPORT" mode with CONSULT-II.
  6. Touch "START ".
  7. When the following conditions are met, "TESTING" will be displayed on the CONSULT-II screen. Maintain the conditions continuously until "TESTING" changes to "COMPLETED". (It will take at least 30 seconds .) ENG SPEED: 1,000 - 3,000 rpm Selector lever: Suitable position Vehicle speed: 36 - 120 kph (22 - 75 MPH) B/FUEL SCHDL: 0.5 - 3.1 msec. If "TESTING" is not displayed after 5 minutes , retry from step 3).
  8. Make sure that "OK" is displayed after touching "SELF-DIAG RESULTS". If "NG" is displayed, refer to "DIAGNOSTIC PROCEDURE". OR

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OVERALL FUNCTION CHECK

Without Consult

  1. Remove vacuum cut valve and vacuum cut valve bypass valve as an assembly.
  2. Apply vacuum to port A and check that there is no suction from port B.
  3. Apply vacuum to port B and check that there is suction from port B.
  4. Blow air in port B and check that there is a resistance to flow out of port A.
  5. Supply battery voltage to the terminal.
  6. Blow air in port A and check that air flows freely out of port B.
  7. Blow air in port B and check that air flows freely out of port A.
  8. If NG, go to "DIAGNOSTIC PROCEDURE".

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DIAGNOSTIC PROCEDURE

COMPONENT INSPECTION

Vacuum cut valve bypass valve
Check air passage continuity

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With Consult
Perform "VC/V BYPASS/V" in "ACTIVE TEST" mode.

OR

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Without Consult
If NG or operation takes more than 1 second , replace vacuum cut valve bypass valve.

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Vacuum cut valve
Check vacuum cut valve as follows:

  1. Plug port C and D with fingers.
  2. Apply vacuum to port A and check that there is no suction from port B.
  3. Apply vacuum to port B and check that there is suction from port A.
  4. Blow air in port B and check that there is a resistance to flow out of port A.
  5. Open port C and D.
  6. Blow air in port check that air flows freely out of port C.
  7. Blow air in port B check that air flows freely out of port D.
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