Powertrain, generic · Auxiliary emission controls

P04C9 Fuel Fill Door Open Request Sensor/Switch Performance/Stuck Off

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

On plug-in hybrids with a sealed, pressurised tank, pressing the fuel button (open request) starts a refuelling mode: the module opens the tank valve, releases the pressure into the charcoal canister and only then unlocks the filler door via an electric actuator (Ford patent). P04C9 means the button gives no or no plausible signal when it should be pressed, or the door is found open without a button press – as after use of the emergency release. No manufacturer document available to us uses this code; the description follows CARB's rules for input and output components and patents on the door actuator.

Likely causes

Fuel button faulty
Wire between button and module open
Door opened via the emergency release
Button ground open

Symptoms

  • Fuel button has no effect, door does not open
  • Refuelling system message in the instrument cluster
  • Refuelling only via emergency release

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–200
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel door open request switchswitch wiringengine control module

Related codes

P04C8P04CAP04CBP04CCP04CDP04BF

References: law.cornell.edu, patents.google.com, mitsubishitechinfo.com.