P0455 on Ford

P0455 is a large (gross) EVAP leak. On late-model Escapes the leading cause is the capless fuel filler inlet — debris or a worn internal flap prevents the neck from sealing, and a 'Check Fuel Fill Inlet' dash message is a dead giveaway the leak is at the filler rather than under the hood. A stuck-open or failed canister purge valve is the other common source. Ford issued TSB 21-2020 for some 2020 Escapes built before March 20, 2020, where a PCM software update corrects a P0455 combined with an inaccurate fuel gauge; SSM 46525/49313 also address EVAP concerns. Older V6 cars can leak at the vent hose or canister.

A very common check-engine cause on the Explorer is an EVAP small-leak code, most often from a stuck or leaking canister purge valve, but also from the capless fuel filler seal, vent valve, or a loose/faulty gas cap. The purge valve controls fuel-vapor flow from the charcoal canister to the intake; when it sticks open or leaks it sets a small/medium EVAP leak code. It rarely affects drivability but will fail emissions testing and, if stuck open, can cause rough idle or hard hot-starts.

The EVAP canister purge valve (purge solenoid) on F-150s commonly sticks in the open position, allowing raw fuel vapor from the charcoal canister to be pulled into the intake when it shouldn't be. This floods the cylinders with vapor — owners report a vehicle that cranks but won't start (or stumbles badly) immediately after filling the tank, then runs fine once it clears. A stuck-open or leaking purge valve, along with cracked/collapsed lines between the canister, valve, and intake manifold, is the most common trigger for P0496 (EVAP flow during a non-purge condition) and a frequent cause of P0455/P0442 large/small leak codes. Ford issued TSB 19-2132 covering loose EVAP hose connections on 2018-2019 trucks. The check-engine light is the usual first symptom; drivability impact ranges from none to hard-start/rough-idle. The real OEM purge valve part number is AU5Z-9C915-B (aftermarket cross-refs: Dorman 911-222, Standard CP1-prefix units).

The under-hood evaporative-emissions purge valve on 2010-2011 Fusion/Milan (2.5L DOHC and 3.0L) built on or before 3/4/2011 can stick open or leak, unmetered vapor entering the intake. This lights the MIL and sets a cluster of EVAP and lean/fuel-trim codes, and can cause rough idle or hard starts. It is a documented Ford pattern failure with a related TSB covering the affected build range.

S197 Mustangs from the mid-2000s have a documented pattern of fuel tank cracking or leaking, often near the seam or around the evaporative emissions components. Owners report strong fuel odor in garages, visible dripping after fill-ups, and EVAP-related warning lights. Because the issue involves fuel leakage near the rear of the vehicle, it presents a fire risk and can require full tank replacement.

Older Rangers in corrosion-prone regions frequently develop rusted fuel filler necks and weakened fuel tank straps. Owners report fuel smells, visible leaks while filling, EVAP faults, or in severe cases a sagging tank due to strap corrosion. This is both a drivability and fire-risk concern, and it appears repeatedly in owner complaints and service discussions for aging trucks.