2001 Infiniti Q45 BaseFACTORY OEM SERVICE PROCEDURE

DTC P0450: EVAP Control System Pressure Sensor (EVAP-CSPS): Procedure

  1. Check EVAP-CSPS hose for blockage or poor connection. Repair as necessary and retest system. If hose is okay, turn ignition off. Loosen and retighten 2 engine ground bolts. See Figure. Disconnect EVAP-CSPS harness connector. See Figure. Inspect connector for water. If water exists, repair or replace connector and retest system. If water does not exist, turn ignition on. Measure voltage between engine ground and EVAP-CSPS harness connector terminal No. 3 (Brown/White wire). If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short between ECM and EVAP-CSPS. Retest system.
  2. 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. See WIRING DIAGRAMS article. Repair circuit as necessary and retest system. If ground circuit is okay, go to next step.
  3. Disconnect ECM harness connector. See Figure. Check continuity between EVAP-CSPS harness connector terminal No. 2 (White wire) and ECM harness connector terminal No. 92 (Light Green wire). 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.
  4. Disconnect EVAP-CPVCV harness connector. See Figure. Measure resistance between the following EVAP-CPVCV terminals:
    • Terminals No. 2 and 1.
    • Terminals No. 2 and 3.
    • Terminals No. 5 and 4.
    • Terminals No. 5 and 6.

    See Figure. Resistance should be about 35-43 ohms at 77°F (25°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP-CPVCV and retest system.

  5. Reconnect EVAP-CPVCV harness connector. Remove EVAP-CPVCV from intake manifold. Disconnect and plug hoses. While observing EVAP-CPVCV shaft, turn ignition on and off. EVAP-CPVCV shaft should move smoothly forward and backward, according to ignition switch position. If operation is as specified, go to next step. If operation is not as specified, replace EVAP-CPVCV and retest system.
  6. Remove EVAP-CVCV. Using jumper wires, apply battery voltage between EVAP-CVCV terminals. See Figure. Check for airflow between ports "A" and "B". Air should not flow. Remove jumper wires. Air should flow. EVAP-CVCV should switch in one second or less. Replace EVAP-CVCV if it does not operate as specified, or if rust exists in port "B". If EVAP-CVCV is okay, go to next step.
    7. CAUTION: DO NOT apply more than 5.91 in. Hg of vacuum to EVAP-CSPS. DO NOT reuse any EVAP-CSPS that has been dropped from a height of 20" (.5 m) or more onto a hard surface such as concrete.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.