Circuit Description

Vapor pressure sensor, canister closed valve Vacuum Switching Valve (VSV) and pressure switching valve VSV are used to detect faults in EVAP system. DTC P0450 is set if 10 seconds after engine starts, vapor pressure sensor reading stays unchanged. DTC P0451 is set if pressure reading at vapor pressure sensor is greater than or equal to pressure of charcoal canister while vehicle is standing at idle and pressure switching valve VSV is off. Possible causes are:

• Short or open in vapor pressure sensor circuit.
• Faulty vapor pressure sensor.
• Faulty ECM.