DTC P0455: Evaporative Emission System Leak Detected (Gross Leak/No Flow)

P0455 - EVAPORATIVE EMISSION SYSTEM LEAK DETECTED (GROSS LEAK/NO FLOW)

Description: The PCM monitors the complete evaporative emission (EVAP) control system for no purge flow, the presence of a large fuel vapor leak, or multiple small fuel vapor leaks. This DTC sets when no purge flow, which is attributed to fuel vapor blockages or restrictions, a large fuel vapor leak, or multiple fuel vapor leaks are detected by the EVAP running loss monitor test with the engine running, but not at idle.
Possible Causes: Damaged, missing or loosely installed fuel filler cap Aftermarket EVAP hardware that does not conform to the required specifications Disconnected or cracked fuel EVAP canister tube, EVAP canister purge outlet tube, or EVAP return tube EVAP purge valve stuck closed Capless fuel tank filler pipe damaged or not sealed correctly (if equipped) Blockages or restrictions in the fuel vapor hoses/tubes Loose fuel vapor hose/tube connections to the EVAP system components Fuel vapor control valve tube assembly or fuel vapor vent valve assembly blocked EVAP canister vent valve stuck open (if equipped) Mechanically inoperative fuel tank pressure (FTP) sensor (if equipped) Damaged EVAP canister
Diagnostic Aids: Check for audible vacuum noise or significant fuel odor in the engine compartment or near the EVAP canister and fuel tank. Verify the capless fuel tank filler pipe is sealed correctly. Install and remove the supplemental fueling adapter five times in the capless fuel tank filler pipe to clear debris on the seal. Refer to the Owner Literature for the location of the supplemental fueling adapter in the vehicle.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Fiesta	GO to PINPOINT TEST HZ .
All others	GO to PINPOINT TEST HX .