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Home >> Nissan-Datsun >> 2001 >> Quest GLE >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0450: EVAP Control System Pressure Sensor >> Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition off. Check vacuum hose connected to EVAP-CSPS for damage and blockage. See Figure. Repair or replace hose as necessary and retest system. If hose is okay, go to next step.
  2. Loosen and retighten engine ground bolts. See Figure. Disconnect EVAP-CSPS harness connector. If water exists in connector, repair or replace connector as necessary and retest system. If connector is okay, go to next step.
  3. Turn ignition on. Measure voltage between ground and EVAP-CSPS harness connector terminal No. 3 (Brown wire). If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short in Brown wire between ECM and EVAP-CSPS, then retest system.
  4. Turn ignition off. Check continuity between ground and EVAP-CSPS harness connector terminal No. 1 (Green wire). Continuity should exist. Also, check circuit for short to voltage. See WIRING DIAGRAMS article. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
  5. Disconnect ECM harness connector. See Figure. Check continuity of Red wire between EVAP-CSPS harness connector terminal No. 2 and ECM harness connector terminal No. 62. See Figure. Also, check circuit for short to ground and short to voltage. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
  6. Disconnect vacuum hoses from EVAP-CPVCV. See Figure. Disconnect EVAP-CPVCV harness connector. Apply air pressure to port "A" at EVAP-CPVCV. See Figure. Air should not flow from port "B". Using fused jumper wires, apply battery voltage between EVAP-CPVCV terminals (component side). Air should now flow from port "B". If EVAP-CPVCV does not operate as specified or operation takes more than one second, replace EVAP-CPVCV and retest system. If EVAP-CPVCV operates as specified, go to next step.
  7. Remove EVAP-CVCV. Check EVAP-CVCV for rust and damage. Rust should not exist in port "B". See Figure. If problem exists, replace EVAP-CVCV. If problem does not exist, go to next step.
  8. Using fused jumper wires, apply battery voltage between EVAP-CVCV terminals (component side). See Figure. Air applied to port "A" should not flow from port "B". Remove jumper wires. Air applied to port "A" should now flow from port "B". If EVAP-CVCV does not operate as specified or operation takes more than one second, go to next step. If EVAP-CVCV operates as specified, go to step  10.
  9. Clean EVAP-CVCV ports with compressed air. Repeat step  8. If EVAP-CVCV still does not operate as specified, replace EVAP-CVCV and retest system. If EVAP-CVCV operates as specified, test is complete.
    10. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  10. Reconnect all harness connectors. 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. 62 (Red wire) by backprobing. See 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 and retest system.
  11. Check hose connected to EVAP-CVCV for blockage. Repair or replace hose as necessary and retest system. If hose is okay, go to next step.
  12. Remove EVAP canister with EVAP-CVCV attached. Turn EVAP canister so EVAP-CVCV is pointing down. If water drains out, go to next step. If water does not drain out, go to step  14.
  13. Weigh EVAP canister with EVAP-CVCV attached. If weight is less than 4 lbs. (1.8 kg), go to next step. If weight is 4 lbs. (1.8 kg) or more, check EVAP canister for damage. Also, check hose between EVAP canister and water separator for clogging or poor connection. Repair hose or replace EVAP canister as necessary and retest system.
  14. Connect all disconnected harness connectors. Disconnect Gray, 8-pin connector M-119 located near EVAP canister. Check continuity between ground and connector M-119 terminal No. 5 (Black/Red wire). See Fig 1. Continuity should exist. Also, check circuit for short to voltage. See WIRING DIAGRAMS article. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
  15. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
Fig 1: Identifying Connector M-119 Terminals
G99B51889Courtesy of NISSAN MOTOR CO., U.S.A.
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