P04F0 EVAP purge flow is not as expected when the engine is under high load (purge line A)

EVAP system high load purge line performance

Monitor

Kelley Blue Book says a car with this code is almost always drivable but the repair should be prioritised, and the Ford bulletins for it describe a lit check engine light caused by loose or partly connected EVAP parts.

It gets more serious if:

  • Inspect soon: Inspect soon if there is a strong fuel smell or the engine lags and sputters under load. One Bronco Sport owner still had lag and sputter after the purge valve was replaced.

Source: how we rate severity

P04F0 in short

P04F0 means the computer sees the EVAP purge system moving fuel vapour into the engine differently than expected at high load. The usual causes are a loose or disconnected vapour line, a sticking purge valve or a fuel cap problem. The car almost always drives normally, but have it checked soon.

The EVAP system stores fuel vapour in a charcoal canister and the computer opens the purge valve so the engine draws that vapour in and burns it. P04F0 is set when the purge flow does not match what the computer commanded at high engine load.

Ford has issued bulletins for 2017-2019 Escape and MKC and 2018-2019 F-150, Expedition and Navigator where the code, often with P144C, is traced to loose or partly connected EVAP vapour lines. Volkswagen lists the code in its EVAP bulletins for 2009-2016 models.

A purge valve that sticks closed is the other repeat finding in owner complaints, but Ford also reports that many returned purge valves tested fully functional, so test before replacing it.

Most likely causes

  1. Loose, cracked or partly connected EVAP vapour line

    Supported by vehicle data
    Why it ranks here
    Ford bulletins TSB 19-2171 and 19-2132 name loose or partly connected EVAP components for this code, and KBB lists loose or damaged EVAP hoses first.
    What would change this
    Rises if a line is found off its fitting or smoke shows a leak at the purge line. Falls if all lines are tight and the leak test passes.
    How to test the vacuum hoses and intake leaks

  2. EVAP purge valve sticking or not flowing

    Supported by vehicle data
    Why it ranks here
    Two Ford owners report a dealer finding the purge valve at fault for P04F0 (one stuck closed), and KBB lists the valve as a cause. Ford service bulletin SSM 50306 warns that many replaced valves tested fine, so confirm first.
    What would change this
    Rises if the valve does not click or flow when commanded and holds vacuum when it should be open. Falls if it flows normally.
    How to test the evap canister purge valve

  3. Fuel cap, capless filler or canister vent fault

    Common general cause
    Why it ranks here
    KBB lists the fuel cap or capless filler and the canister or vent valve among the causes of the same purge-line performance fault.
    What would change this
    Rises if the cap is loose, damaged or the code appeared after refuelling. Falls if the cap and filler seal correctly.
    How to test the fuel (gas) cap

  4. Fuel tank pressure sensor unseated (2021-2022 F-150)

    Supported by vehicle data
    Why it ranks here
    Ford bulletin SSM 50614 says the fuel tank pressure sensor can come unseated from its mount on the EVAP assembly and set P04F0 and/or P04EE on 2021-2022 F-150.
    What would change this
    Rises on a covered F-150 with P04EE stored too. Falls on any other vehicle.
    How to test the fuel tank pressure sensor

  5. Crankcase ventilation (PCV) fault on the same engine

    Possible — needs testing
    Why it ranks here
    One 2022 Tiguan owner reports P04F0 together with a crankcase ventilation failure. This is a single report, so it is only worth testing after the EVAP side checks out.
    What would change this
    Rises if the PCV valve or hoses are damaged or oil is in the intake. Falls if the crankcase vent system checks out.
    How to test the crankcase ventilation (pcv) valve

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes and freeze-frame data with a scan tool. Note whether P144C, P0441, P0442, P0455 or P0456 are stored with P04F0.

    Low riskTool: OBD-II scan tool

    • IfP144C is stored too on a Ford

      It meansFord groups these two codes in the same bulletins.

      Go to step 2

    • IfP04F0 is alone or with other EVAP codes

      It meansContinue to the visual check.

      Go to step 3

  2. Ask a dealer whether your VIN is covered by an EVAP line, purge valve or software bulletin for P04F0 (Ford, Volkswagen).

    Low risk

  3. With the engine off and cool, check the fuel cap seal and look along the EVAP lines from the tank, canister and purge valve for loose, cracked or unplugged connections.

    Low risk

  4. Command the purge valve on and off with a bidirectional scan tool and check that it opens, closes and holds vacuum.

    Use cautionTool: bidirectional scan tool, hand vacuum pump

    Warning:Fuel vapour is flammable. Work away from sparks and let a shop do the test if you are not sure.

  5. Have the EVAP system smoke-tested, including the fuel tank pressure sensor mount on an F-150, and check the PCV system if the engine is a VW.

    Best left to a shopTool: EVAP smoke machine

    Warning:Smoke testing uses a pressurised fuel system. Leave it to a shop.

Symptoms

  • Check engine light with no change in how the car drives
  • Slight lag or hesitation under hard acceleration Gets more serious: stop and have it checked.
  • Strong fuel smell around the car Gets more serious: stop and have it checked.

Compare with: Check engine light came on after getting gas

How to fix

  1. Check that the fuel cap clicks tight and the seal is not cracked.

  2. Ask a dealer whether your VIN has an open EVAP or software bulletin for P04F0.

Parts and cost context

  • EVAP canister purge valve:Ford says many valves returned for this code tested fine, so confirm the valve is at fault before buying one. Labour varies; get a quote.
  • Fuel (gas) cap:A cap is cheap to replace and worth ruling out first.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2017–2019 · Escape

    Supported by vehicle data

    Ford bulletin TSB 19-2171 ties P04F0 (often with P144C) to loose or partly connected EVAP components on EcoBoost Escapes. Whether the bulletin is still current is not verified.

  • 2018–2019 · F-150

    Supported by vehicle data

    Ford bulletin TSB 19-2132 ties P04F0 and/or P144C to loose or partly connected EVAP components. Whether the bulletin is still current is not verified.

  • 2021–2022 · F-150

    Supported by vehicle data

    Ford service bulletin SSM 50614 says the fuel tank pressure sensor can become unseated from the EVAP assembly and set P04F0 and/or P04EE.

  • 2022 · Bronco Sport

    Supported by vehicle data

    One owner reports a dealer finding the purge valve sticking closed for P04F0. Complaint signal only; no bulletin.

  • TSB19-2171 (ford)Status unverified

    MIL on with P04F0 and/or P144C

    2017–2019escape · NHTSA 10160819

    Loose or partly connected EVAP components on the 1.5L, 2.0L and 2.3L EcoBoost engines.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • TSB19-2132 (ford)Status unverified

    MIL on with P04F0 and/or P144C

    2018–2019f-150, expedition · NHTSA 10160865

    Loose or partly connected EVAP components.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM 50614Status unverified

    MIL on with P04F0 and/or P04EE

    2021–2022f-150 · NHTSA 10209219

    The fuel tank pressure sensor can become unseated from its mount on the EVAP assembly.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM 50306Status unverified

    MIL on with P0496, P0456, P0455, P04F0 and/or P0451

    2018–2022expedition, escape · NHTSA 10204040

    Returned purge valves tested fully functional; check before replacing the valve.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Volkswagen

  • 2009–2016 · Jetta

    Supported by vehicle data

    Volkswagen bulletin 2034072 was updated to include P04F0. The NHTSA summary does not say what the repair is.

  • 2034072Status unverified

    EVAP bulletin updated to include P04F0

    2009–2016cc, jetta, touareg, tiguan, beetle, gti · NHTSA 10125657

    The NHTSA summary says only that P04F0 was added to this bulletin.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P144COn Ford vehicles, the EVAP purge check valve or vapor ejector path is not performing

    Shares causes Supported by vehicle data

    Ford bulletins list P04F0 and P144C together for loose or partly connected EVAP parts on the Escape, MKC, F-150, Expedition and Navigator.

  • P0442EVAP system small leak detected

    Same system Possible — needs testing

    Volkswagen lists P04F0 and P0442 (small EVAP leak) as separate concerns in the same bulletins, so check the EVAP system for leaks when either shows.

  • P0455EVAP system large leak detected

    Same system Supported by vehicle data

    Ford service bulletin SSM 50306 covers P04F0 alongside P0455 and P0456 on the same vehicles.

All EVAP (evaporative emissions) codes

P04F0 questions

Can I keep driving with P04F0?

Usually yes. Kelley Blue Book says the car is almost always drivable, but have it checked soon, and sooner if you smell fuel or the engine lags under load.

Is P04F0 a bad purge valve?

Sometimes. Owners report purge valves replaced for it, but Ford says many returned valves tested fine and loose vapour lines are the more common bulletin finding. Test before replacing.

Sources and review

  1. P04F0 code: EVAP system high load purge line A performance — Kelley Blue Book (KBB Service Advisor)
  2. Ford TSB 19-2171: P04F0 and/or P144C (2017-2019 Escape and MKC) — Ford Motor Company / NHTSA
  3. NHTSA complaint ODI 2110665: 2022 Ford Bronco Sport, P04F0 — NHTSA Office of Defects Investigation (owner complaint)
  4. Ford TSB 19-2132: P04F0 and/or P144C (2018-2019 F-150, Expedition, Navigator) — Ford Motor Company / NHTSA
  5. NHTSA complaint ODI 1834669: 2020 Ford Escape, P04F0 — NHTSA Office of Defects Investigation (owner complaint)
  6. Ford SSM 50306: MIL with P0496, P0456, P0455, P04F0 and/or P0451 — Ford Motor Company / NHTSA
  7. Ford SSM 50614: MIL with P04F0 and/or P04EE (2021-2022 F-150) — Ford Motor Company / NHTSA
  8. NHTSA complaint ODI 2123608: 2022 Volkswagen Tiguan, P04F0 — NHTSA Office of Defects Investigation (owner complaint)
  9. Volkswagen bulletin 2034072 (V201702): DTC P04F0 added — Volkswagen of America / NHTSA
  10. Volkswagen bulletin VIN4APIN20230517: MIL-on with P04F0 and P0456/P0442 stored — Volkswagen of America / NHTSA
Last reviewed
Written by
Saurabh K.
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