Possible Causes

ECM illuminates MIL and sets DTC P0456, when EVAP control system has a very small leak or does not operate properly. Possible causes are:

• Fuel filler cap remains open or fails to close.
• Incorrect fuel tank vacuum relief valve.
• Incorrect fuel filler cap.
• Foreign matter in fuel filler cap.
• Leak in hose between intake manifold and EVAP-CPVCSV.
• Foreign matter in EVAP Canister Vent Control Valve (EVAP-CVCV).
• Leak in EVAP canister or fuel tank.
• Leak or blockage in EVAP purge line.
• Leak or blockage in hose to EVAP Control System Pressure Sensor (EVAP-CSPS).
• Defective EVAP-CVCV or circuit.
• Defective EVAP-CPVCSV or circuit.
• Poor, loose, corroded or damaged terminal connections.
• Defective absolute pressure sensor.
• Defective fuel tank temperature sensor.
• Missing or damaged EVAP-CVCV "O" ring.
• Defective EVAP-CSPS.
• Defective fuel level sensor or circuit.
• EVAP canister saturated with water.
• Defective water separator.
• Defective refueling control valve.
• Leak in On-Board Refueling Vapor Recovery (ORVR) system.