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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - Self-Diagnostics - 1.8L - XE, GXE) >> Diagnostic Tests >> DTC P1491: Vacuum Cut Valve By-Pass Valve >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.

  1. Check Vacuum Cut Valve By-Pass Valve Operation

    Remove vacuum cut valve and vacuum cut valve by-pass valve as an assembly, leaving harness connected. See Figure . Apply vacuum to port "A". See Fig 1 . Vacuum should not exist at port "B". Apply vacuum to port "B". Vacuum should exist at port "A". Blow air in port "B". Air should flow out of port "A" with some resistance.

    1. With CONSULT-II

      Turn ignition on. Select VC/V BYPASS/V in ACTIVE TEST mode with CONSULT-II. Press ON. Air should flow freely through vacuum cut valve ports "A" and "B" in both directions. If operation is as specified, go to next step. If operation is not as specified, go to step  5 .

    2. Without CONSULT-II

      Disconnect vacuum cut valve by-pass valve harness connector. Using jumper wires, apply battery voltage to by-pass valve terminals. Air should flow freely through ports "A" and "B" in both directions. If operation is as specified, go to next step. If operation is not as specified, go to step  5 .

  2. Check EVAP Purge Line

    Check purge line between EVAP canister and fuel tank for blockage or leak. If problem is found, clean or repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If problem is not found, go to next step.

  3. Check EVAP Purge Port

    Check purge port on fuel tank for clogging. Clean purge port as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If purge port is okay, go to next step.

  4. Check EVAP Canister

    Remove hoses from EVAP canister ports "A" and "B". See Fig 2 . Pinch EVAP-CVCV hose and blow air into port "A". Air should flow freely out of port "B". If operation is as specified, go to step  6 . If operation is not as specified, replace EVAP canister. Perform DTC CONFIRMATION TEST  to verify repair.

  5. Check By-Pass Hoses

    Remove by-pass hoses from vacuum cut valve. Check hoses for blockage. If blockage exists, clean or replace hoses as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If by-pass hoses are okay, go to next step.

  6. Check Vacuum Cut Valve By-Pass Valve

    Check vacuum cut valve by-pass valve as shown in illustration. See Figure . If vacuum cut valve by-pass valve is okay, go to next step. If vacuum cut valve by-pass valve is not okay, replace vacuum cut valve by-pass valve. Perform DTC CONFIRMATION TEST  to verify repair.

  7. Check Vacuum Cut Valve

    Check vacuum cut valve as shown in illustration. See Figure . If vacuum cut valve is okay, go to next step. If vacuum cut valve is not okay, replace vacuum cut valve. Perform DTC CONFIRMATION TEST  to verify repair.

  8. Check EVAP-CSPS Hose

    Turn ignition off. Check for disconnection or improper connection of hose connected to EVAP-CSPS. See Figure . If problem is found, repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If problem is not found, go to next step.

  9. Check EVAP-CSPS Connector

    Disconnect EVAP-CSPS harness connector. Check connectors for water. If water exists, replace EVAP-CSPS. Perform DTC CONFIRMATION TEST  to verify repair. If water does not exist, go to next step.

  10. Check EVAP-CSPS

    Check EVAP-CSPS as shown in illustration. See Figure . If EVAP-CSPS is okay, go to next step. If EVAP-CSPS is not okay, replace EVAP-CSPS. Perform DTC CONFIRMATION TEST  to verify repair.

  11. Check EVAP-CVCV Hose

    Disconnect hose connected to EVAP-CVCV. See Figure . Check hose for clogging. If problem is found, repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If problem is not found, go to next step.

  12. Check EVAP-CVCV

    Check EVAP-CVCV as shown in illustration. See Figure . If EVAP-CVCV is okay, go to next step. If EVAP-CVCV is not okay, replace EVAP-CVCV. Perform DTC CONFIRMATION TEST  to verify repair.

  13. Check For Intermittent

    Check for intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. Perform DTC CONFIRMATION TEST  to verify repair.
Fig 1: Testing Vacuum Cut Valve & Vacuum Cut Valve By-Pass Valve
G99G08867Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Testing EVAP Canister
G00172728Courtesy of NISSAN MOTOR CO., U.S.A.
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