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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 112 (Engine Controls Self-Diagnostics - Pathfinder) >> Diagnostic Tests >> DTC P1491: Vacuum Cut Valve By-Pass Valve - Does Not Operate Properly >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
  1. If using CONSULT-II, go to next step. If using generic scan tool, go to step  3.
  2. Turn ignition off. 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. 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 step  4. If operation is not as specified, go to step  7.
  3. 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. 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  7.
  4. Check purge line between EVAP canister and fuel tank for blockage or leak. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  5. Check EVAP purge port on fuel tank for blockage. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  6. 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  14. If operation is not as specified, replace EVAP canister. After repair, repeat appropriate DTC confirmation test.
  7. Remove by-pass hoses from vacuum cut valve. Check hoses for blockage. If no problem is found, go to next step. If problem is found, repair or replace hoses as necessary. After repair, repeat appropriate DTC confirmation test.
  8. If using CONSULT-II, go to next step. If using generic scan tool, go to step  10.
  9. Reconnect all harness connectors. Turn ignition on. Perform VC/V BYPASS/V in ACTIVE TEST mode with CONSULT-II. When VC/V BYPASS/V is ON, air should flow between ports "A" and "B". See Figure. When VC/V BYPASS/V is OFF, air should not flow through vacuum cut valve by-pass valve. Valve should switch in less than one second. If operation is as specified, go to step  11. If operation is not as specified, replace vacuum cut valve by-pass valve. After repair, repeat appropriate DTC confirmation test.
  10. Remove vacuum cut valve by-pass valve. Using jumper wires, apply battery voltage to vacuum cut valve by-pass valve terminals. See Figure. Air should flow between ports "A" and "B". Remove jumper wires. Air should not flow. Valve should switch in less than one second. If operation is as specified, go to next step. If operation is not as specified, replace vacuum cut valve by-pass valve. After repair, repeat appropriate DTC confirmation test.
  11. Plug vacuum cut valve ports "C" and "D" with fingers. See Figure. Apply vacuum to port "A". 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. Remove fingers from ports "C" and "D". Blow air in port "A". Air should flow freely out of port "C". Blow air in port "B". Air should flow freely out of port "D". If operation is as specified, go to next step. If operation is not as specified, replace vacuum cut valve. After repair, repeat appropriate DTC confirmation test.
  12. Check for disconnection or improper connection of hose connected to EVAP Control System Pressure Sensor (EVAP-CSPS). See Figure. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  13. Disconnect EVAP-CSPS harness connector. Check for water damage to EVAP-CSPS connectors. If water damage does not exist, go to next step. If water damage exists, replace EVAP-CSPS. After repair, repeat appropriate DTC confirmation test.
    14. CAUTION: DO NOT apply more than 5.91 in. Hg (20 kPa) of vacuum to EVAP-CSPS. Replace EVAP-CSPS if it has been dropped from a height of more than 20" (.5 m) onto a hard surface such as concrete.
    CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  14. Remove EVAP Control System Pressure Sensor (EVAP-CSPS) with its harness connector connected. See Figure. Turn ignition on. Using a hand vacuum pump, apply 2.76 in. Hg (9.3 kPa) of vacuum to EVAP-CSPS. Backprobing at ECM, measure voltage between ground and ECM terminal No. 32 (Blue/Green wire). See Figure and Figure . With 2.76 in. Hg (9.3 kPa) of vacuum applied to EVAP-CSPS, voltage should be .4-.6 volt. When vacuum is removed, voltage should be 3.0-3.6 volts. If voltage is as specified, go to next step. If voltage is not as specified, replace EVAP-CSPS. After repair, repeat appropriate DTC confirmation procedure.
  15. Disconnect hose connected to EVAP Canister Vent Control Valve (EVAP-CVCV). See Figure. Check hose for blockage If blockage does not exist, go to next step. If blockage exists, clean hose with compressed air. After repair, repeat appropriate DTC confirmation procedure.
  16. Remove EVAP-CVCV. Check for rust in port "B". See Figure. If rust does not exist, go to next step. If rust exists, replace EVAP-CVCV. After repair, repeat appropriate DTC confirmation procedure.
  17. If using CONSULT-II, go to next step. If using generic scan tool, go to step  19.
  18. Reconnect all harness connectors. Turn ignition on. Perform VENT CONTROL/V in ACTIVE TEST mode with CONSULT-II. When VENT CONTROL/V is ON, air should not flow between ports "A" and "B". When VENT CONTROL/V is OFF, air should flow between ports "A" and "B". It should take less than one second for valve to open or close. If operation is as specified, go to step  20. If operation is not as specified, clean EVAP-CVCV with compressed air, and retest. If operation is still not as specified, replace EVAP-CVCV. After repair, repeat appropriate DTC confirmation procedure.
  19. Disconnect EVAP-CVCV 2-pin harness connector. Using jumper wires, apply battery voltage to EVAP-CVCV terminals. See Figure. When voltage is applied, air should not flow between ports "A" and "B". Remove jumper wires. Air should flow. EVAP-CVCV should switch in less than one second. If operation is as specified, go to step  20. If operation is not as specified, clean EVAP-CVCV with compressed air, and retest. If operation is still not as specified, replace EVAP-CVCV. After repair, repeat appropriate DTC confirmation procedure.
  20. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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
G99F51099Courtesy of NISSAN MOTOR CO., U.S.A.
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