OBD Guide
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P04AF

EVAP System Purge Control Valve B Stuck Closed

P04AF is an OBD-II diagnostic trouble code meaning: EVAP System Purge Control Valve B Stuck Closed. Common causes: mechanical jamming of the purge valve solenoid, valve clogged with resinous deposits from the adsorber. Estimated repair cost: $17–78.

Severity
✅ Low
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$17–78 (est.)

Symptoms

  • Check Engine Light Is On
  • Strong smell of gasoline when opening the hood or in the fuel tank area
  • Deteriorating fuel economy
  • Unstable idle
  • Difficulty starting in hot weather (vapor pressure in the tank)
  • Possible activation of the fuel tank safety valve

Causes

  • Mechanical jamming of the purge valve solenoid
  • Valve clogged with resinous deposits from the adsorber
  • Broken valve return spring
  • Corroded valve stem
  • Valve icing in extreme cold (temporary cause)
  • Deformation of the plastic valve body due to fuel exposure

How to Fix

  1. Perform purge valve B activation test via scanner - check if mixture composition changes
  2. Check the valve solenoid: when 12V is supplied directly, the valve should open with a characteristic click
  3. Inspect the valve for resin deposits and body deformation
  4. Check the hose from the adsorber to the valve for blockages
  5. Try cleaning the valve with carburetor cleaner (if the body is not deformed)
  6. Replace purge valve B (mechanical jamming most often requires replacement)
  7. Check the condition of the carbon adsorber - replace if saturated
  8. Reset codes and make sure the purge is normal during a test drive

Related codes

P04ABP04ACP04AEP0440P0441P0446P0455

Error P04AF by Vehicle Brand

AcuraAudiBAICBMWBYDBuickCadillacChanganCheryChevroletChryslerCitroenDodgeDongfengExeedFAWFordForthingFotonGACGMGMCGeelyGreat WallHavalHondaHongqiHyundaiInfinitiJACJaecooJaguarJeepJetourKaiyiKiaLadaLexusLi AutoLifanLincolnLivanMazdaMercedes-BenzMercuryMitsubishiNIONissanOldsmobileOmodaOpelPeugeotPlymouthPontiacRenaultSWMSaturnSkodaSkywellSubaruSuzukiTankToyotaVolkswagenVolvoVoyahXPengZeekrZotye

FAQ

What does the P04AF code mean?

P04AF is an OBD-II diagnostic trouble code that indicates: EVAP System Purge Control Valve B Stuck Closed

What causes a P04AF error code?

The most common causes of P04AF include: Mechanical jamming of the purge valve solenoid; Valve clogged with resinous deposits from the adsorber; Broken valve return spring; Corroded valve stem.

How do I fix a P04AF diagnostic trouble code?

To fix P04AF: Perform purge valve B activation test via scanner - check if mixture composition changes. Check the valve solenoid: when 12V is supplied directly, the valve should open with a characteristic click. Inspect the valve for resin deposits and body deformation. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P04AF?

Do not drive — repair immediately

How much does it cost to fix P04AF?

The estimated repair cost for P04AF is $17–78. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat