DTC P0450: EVAP Control System Pressure Sensor: Procedure

1. Check rubber hose to EVAP control system pressure sensor for damage or clogging. Repair as necessary. Loosen and retighten 2 engine ground bolts located on intake manifold near fuel injectors. See Figure. Disconnect EVAP control system pressure sensor harness connector. See Fig 1. Turn ignition on. Using DVOM, measure voltage between EVAP control system pressure sensor harness connector terminal No. 3 (Brown wire) and ground. If voltage is approximately 5 volts, go to next step. If voltage is not approximately 5 volts, check and repair for open or short in Brown wire between PCM and EVAP control system pressure sensor.
2. Turn ignition off. Using DVOM, check continuity between EVAP control system pressure sensor harness connector terminal No. 1 (Black/White wire) and ground. If continuity exists, go to next step. If continuity does not exist, repair open in Black/White wire between PCM and EVAP control system pressure sensor.
3. Leave ignition off. Disconnect PCM harness connector. See Figure. Using DVOM, check continuity between EVAP control system pressure sensor harness connector terminal No. 2 (Yellow wire) and PCM connector terminal No. 62. See Figure. If continuity exists, go to next step. If no continuity exists, repair open or short in Yellow wire between PCM and EVAP control system pressure sensor.
4. Check EVAP canister purge volume control solenoid valve and EVAP canister vent control valve. See DTC P0440 OR P1440:  EVAPORATIVE EMISSION (EVAP) CONTROL SYSTEM. Repair or replace as necessary. If components are okay, go to next step.
5. Remove EVAP control system pressure sensor. Reconnect all harness connectors. Connect vacuum pump to vacuum port. Turn ignition on. Measure voltage between ground and EVAP control system pressure sensor harness connector terminal No. 2 (Yellow wire) by backprobing connector. Without vacuum applied, voltage should be 3.0-3.6 volts. Apply 2.8 in. Hg to sensor. With vacuum applied, voltage should be 0.4-0.6 volt. If voltage is not as specified, replace EVAP control system pressure sensor. If voltage is as specified, go to next step.
6. Check EVAP purge line for cracks. Inspect EVAP system components for damage or poor connections. Remove EVAP canister with EVAP canister vent control valve attached. See VACUUM DIAGRAMS article for canister location. Turn EVAP canister over and check for water leaking from EVAP canister vent control valve. If water is not leaking from valve, go to next step. If water is leaking from valve, weigh EVAP canister with valve attached. If canister is less than 4.0 lbs. (1.8 kg), go to next step. If canister is equal to or more than 4.0 lbs. (1.8 kg), replace EVAP canister and retest system.
7. Disconnect and reconnect harness connectors in circuit. Check PCM connector for damage or corrosion. Repair as necessary.

Fig 1: Locating EVAP Control System Pressure Sensor

Courtesy of NISSAN MOTOR CO., U.S.A.