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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 38 (Engine Controls - Self-Diagnostics) >> 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 Maxima and 2002 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.
  1. 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. If using CONSULT-II, go to next step. If using generic scan tool, go to step  3 .
  2. 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  6 .
  3. 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  6 .
  4. Check purge line between EVAP canister and fuel tank for blockage or leak. Also, check fuel tank purge port for blockage. If problem is found, clean or repair as necessary. If purge line and purge port are okay, go to next step.
  5. 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  12 . If operation is not as specified, replace EVAP canister.
  6. Remove by-pass hoses from vacuum cut valve. Check hoses for blockage. If blockage exists, clean or replace hoses as necessary. If by-pass hoses are okay, go to next step.
  7. If using CONSULT-II, go to next step. If using generic scan tool, go to step  9 .
  8. 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 through vacuum cut valve by-pass valve. 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  10 . If operation is not as specified, replace vacuum cut valve by-pass valve.
  9. Remove vacuum cut valve by-pass valve. Using jumper wires, apply battery voltage to 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.
  10. 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.
  11. Check for disconnection or improper connection of hose connected to EVAP-CSPS. See Figure . If a problem is found, repair as necessary. If no problem is found, disconnect EVAP-CSPS harness connector. If water exists in connector, replace EVAP-CSPS. If water does not exist in connector, go to next step.
    12. 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.
  12. Remove EVAP-CSPS with its harness connector connected. Turn ignition on. Using a hand vacuum pump, apply 2.76 in. Hg of vacuum to EVAP-CSPS. Measure voltage between ground and ECM terminal No. 60 (White wire) by backprobing. See Figure and Figure . Voltage should be .4-.6 volt. Disconnect vacuum pump. 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.
  13. Disconnect hose connected to EVAP-CVCV. See Figure . Check hose for blockage. If blockage exists, clean hose with compressed air. If blockage does not exist, remove EVAP-CVCV. Check for rust in port "B". See Figure . If rust exists, replace EVAP-CVCV. If rust does not exist, go to next step.
  14. If using CONSULT-II, go to next step. If using generic scan tool, go to step  16 .
  15. 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  17 . If operation is not as specified, clean EVAP-CVCV with compressed air, and retest. If operation is still not as specified, replace EVAP-CVCV.
  16. Using jumper wires, apply battery voltage to EVAP-CVCV terminals. See Figure . 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  17 . If operation is not as specified, clean EVAP-CVCV with compressed air, and retest. If operation is still not as specified, replace EVAP-CVCV.
  17. 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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