Circuit Description

Vapor pressure sensor and canister closed valve Vacuum 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 vapor pressure sensor output changes 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.