P0455 on Ford: How to Diagnose & Fix
Evaporative Emission Control System Leak Detected (Gross Leak)
3 Ford models · 3 documented issues · $60-$350 repair
P0455 on Ford by model: symptoms, diagnosis and fix
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.
Common Symptoms
- Check-engine light with EVAP small-leak code
- Occasional fuel smell
- Rough idle or stumble if purge valve stuck open
- Hard hot restart
- Emissions test failure
How to Fix
Start with the cheapest checks: inspect/replace the gas cap and check the capless filler seal. Perform an EVAP smoke test to pinpoint the leak; replace the canister purge valve (or vent valve/canister) as indicated, then clear codes and run the EVAP monitor to confirm.
Sources for this issue (2)
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, letting unmetered vapor into 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. Ford covered the affected build range under safety recall 15V793 (Ford 15S34) because the faulty purge valve can cause abnormal fuel-tank pressure changes that may crack the tank and leak fuel.
Common Symptoms
- Check engine light on
- Rough idle or stalling
- Hard start after refueling
- Fuel smell
- Failed emissions test
How to Fix
Check by VIN whether recall 15V793 (Ford 15S34) is still open: dealers update the PCM, leak-test the canister purge valve, inspect the fuel tank for cracks, and replace the purge valve and tank as necessary free of charge. Confirm the purge valve holds vacuum and clicks when energized; replace the stuck/leaking purge valve (inexpensive part). Verify no cracked EVAP hoses, a properly sealing gas cap, and an intact charcoal canister before clearing codes. Smoke-test the EVAP system if large-leak codes persist.
Sources for this issue (1)
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 or partially connected EVAP vapor lines (DTC P04F0/P144C) on 2018-2019 F-150s with the 2.7L or 3.5L EcoBoost. The check-engine light is the usual first symptom; drivability impact ranges from none to hard-start/rough-idle. The OEM purge valve part number is AU5Z-9C915-B (aftermarket cross-refs: Dorman 911-222, Standard CP1-prefix units).
Common Symptoms
- Check engine light with P0496, P0455, P0442, or P0446
- Hard start or no-start immediately after filling the fuel tank
- Rough or hunting idle that clears after the engine warms
- Slight loss of fuel economy
- Hissing or fuel-vapor smell near the engine
How to Fix
Verify with a smoke test before replacing parts — roughly 30% of P0455/P0456 codes are a loose or cracked gas cap, so reseat/replace the cap and clear first. If the purge valve fails to hold vacuum when commanded closed (it should seal), it is leaking and must be replaced. Inspect the rubber lines from the canister to the valve and to the intake for cracks/collapse and reseat loose connections per TSB 19-2132. After repair, clear codes and complete a drive cycle to allow the EVAP monitor to re-run. The purge valve sits near the throttle body/intake and is a quick R&R; expect roughly $25-$70 for the part plus labor.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- EVAP purge control valve (VMV, with fuel-tube support bracket) — 2017-2020 F-150 3.5L EcoBoost (2nd-gen GTDI)OEMJL3Z-9B325-D (replaces HL3Z-9B325-A / HL34-9B325-AB)Cross-refNOVAPARTS JL3Z-9B325-D (aftermarket copy)$69–$127
On the 2nd-gen 3.5L EcoBoost (2017-2020) the purge valve is sold by Ford as a valve + bracket unit under the 9B325 base number (catalog title reads 'Bracket - Fuel Tube Support, also includes VMV valve'). Ford catalog lists it for 2017-2…
- EVAP purge control valve (VMV, with fuel-tube support bracket) — 2018-2020 F-150 2.7L EcoBoost V6OEMJL3Z-9B325-CCross-refFANLIDE JL3Z-9B325-C (aftermarket copy)$76–$101
For 2015-2017 2.7L EcoBoost trucks Ford's catalog shows no standalone purge valve, only the FL3Z-9F945-C valve assembly (~$390) — those owners should verify by VIN at a dealer.
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Sources for this issue (1)
P0455 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0455 mean on a Ford?
P0455 stands for "Evaporative Emission Control System Leak Detected (Gross Leak)." This code means your car's evaporative emission (EVAP) system has detected a large (gross) leak, so fuel vapors that should be sealed inside the fuel and vapor system are escaping into the atmosphere. The EVAP system captures gasoline vapors from the tank and routes them to the engine to be burned instead of polluting the air, and the computer periodically pressure- or vacuum-tests this sealed system. A gross leak almost always points to something obvious and easy, like a loose, missing, or bad gas cap, rather than a deep mechanical failure. It rarely affects how the car drives, but it should be fixed to pass emissions and stop wasting fuel vapor. On Ford it is documented across 3 models: Explorer, Fusion, F-150.
What are the most common causes of P0455?
The most common causes of P0455 are: Loose, missing, or improperly tightened gas cap, Worn, cracked, or failed gas cap seal, Cracked or disconnected EVAP/vapor hose, Damaged or missing fuel filler neck seal, Faulty EVAP purge valve stuck open, Failed EVAP vent valve, Cracked or damaged charcoal canister. The specific cause varies by vehicle.
How much does it cost to fix P0455 on a Ford?
Published repair estimates on Ford range from $60 to $350 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.