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Home >> Infiniti >> 2001 >> QX4 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 3.5 >> Diagnostic Tests >> DTC P0450: EVAP Control System Pressure Sensor (EVAP-CSPS) >> Procedure
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DTC P0450: EVAP Control System Pressure Sensor (EVAP-CSPS): Procedure

  1. Check EVAP-CSPS hose for blockage or leak. See Fig 1. Repair as necessary and retest system. If hose is okay, loosen and retighten engine ground bolts. See Figure. Disconnect EVAP-CSPS harness connector. If water exists in connector, repair or replace connector and retest system. If connector is okay, go to next step.
  2. Turn ignition on. Measure voltage between ground and EVAP-CSPS harness connector terminal No. 3 (Pink/Black wire). If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short in Pink/Black wire and retest system.
  3. Turn ignition off. Check continuity between engine ground and EVAP-CSPS harness connector terminal No. 1 (Black wire). Also check circuit for short to voltage. Repair circuit as necessary and retest system. If ground circuit is okay, go to next step.
  4. Disconnect ECM harness connector. See Figure. Check continuity between of Green wire between EVAP-CSPS harness connector terminal No. 2 and ECM harness connector terminal No. 84. See Figure. Also check circuit for short to voltage. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
  5. Remove EVAP-CPVCV. See Figure. Using jumper wires, apply battery voltage to EVAP-CPVCV terminals. See Figure. Check for airflow between ports "A" and "B". Air should flow. Remove jumper wires. Air should not flow. If operation is as specified, go to next step. If operation is not as specified, replace EVAP-CPVCV and retest system.
  6. Check rubber hose to EVAP canister vent control valve for obstructions. Clean or replace hose as required and retest system. If hose is okay, remove EVAP-CVCV. Check for rust in port "B". See Figure. If rust exists, replace EVAP-CVCV and retest system. If rust does not exist, go to next step.
  7. Using jumper wires, apply battery voltage between EVAP-CVCV terminals. Air should not flow between ports "A" and "B". See Figure. Disconnect jumper wires. Air should flow between ports "A" and "B". EVAP-CVCV should switch in one second or less. If EVAP-CVCV operates as specified, go to step  14. If EVAP-CVCV does not operate as specified, go to next step.
  8. Clean EVAP-CVCV ports with compressed air and repeat step  7. If EVAP-CVCV is okay, go to next step. If EVAP-CVCV still does not operate as specified, replace EVAP-CVCV and retest system.
    9. CAUTION: DO NOT apply more than 5.91 in. Hg of vacuum to EVAP-CSPS. DO NOT use ECM ground terminals when measuring voltage. Replace EVAP-CSPS if it has been dropped from a height of more than 20" (.5 m) onto a hard surface such as concrete.
  9. Remove EVAP Control System Pressure Sensor (EVAP-CSPS) with its harness connector connected. Turn ignition on. Using a suitable hand vacuum pump, apply 2.76 in. Hg of vacuum to EVAP-CSPS. Measure voltage between ground and ECM terminal No. 84 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 and retest system.
  10. Remove water separator. See Figure. Visually inspect water separator for blockage or cracks. Inspect hoses for cracks. Repair as necessary and retest system. If no problems are found, go to next step.
    11. CAUTION: DO NOT disassemble water separator.
  11. With water separator port "A" plugged, blow air into port "B". See Figure. Air should flow out of port "C". With port "C" plugged, blow air into port "B". Air should flow out of port "A". If operation is as specified, go to next step. If operation is not as specified, replace water separator and retest system.
  12. Remove EVAP canister with EVAP-CVCV attached. Invert EVAP canister and attempt to drain water from EVAP canister. If water drains from EVAP canister, go to next step. If water does not drain from EVAP canister, go to step  14.
  13. Weigh EVAP canister with EVAP-CVCV attached. If EVAP canister weighs less than 4.0 lbs. (1.8 kg), go to next step. If EVAP canister weighs 4.0 lbs. (1.8 kg) or more, inspect EVAP canister for damage and hoses to water separator for poor connections or blockage. Repair as necessary and retest system.
  14. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
Fig 1: Locating EVAP Control System Pressure Sensor (EVAP-CSPS)
G97F06523Courtesy of NISSAN MOTOR CO., U.S.A.
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