There are multiple causes. The simplest is usually a loose or defective fuel cap. Any loose or broken hose in the evaporative emission system can cause it as well.
Trouble code P0455 means: Evaporative Emission System Leak Detected (gross leak/no flow)
Trouble code P0455 means: EVAP System Gross Leak (0.080") Detected
Trouble code P0455 means: EVAP System Large Leak (0.080") Detected
Trouble code P0455 means:EVAP Large Leak DetectedLarge vapor leak in the evaporative emmisions systemTrouble code P0455 means: Evaporative Emission System Leak Detected (gross leak/no flow)Large vapor leak in the evaporative emmisions system
Two common causes are loose gas cap and cracked hoses between the tank and engine.
Trouble code P0455 means: Evaporative Emission System Leak Detected (gross leak/no flow)
Large EVAP leak
Trouble code P0325 means: Knock Sensor 1 Circuit (Bank 1) Trouble code P0455 means: EVAP System Gross Leak (0.080") Detected
Trouble code P0430 means: Catalyst Efficiency Below Normal (Bank 2) Trouble code P0455 means: EVAP System Gross Leak (0.080") Detected
Trouble code P0455 means:Evaporative emission (EVAP) control system leak detected (no purge flow or large leak)
Trouble code P0455 means: Evaporative Emission System Leak Detected (gross leak/no flow)
Trouble code P0455 means: Evaporative Emission System Leak Detected (gross leak/no flow)