Powertrain, generic · Auxiliary emission controls

P04BF Fuel Fill Door Unlock Control Circuit/Open

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). P04BF concerns the unlock circuit: the module detects an open circuit in the output to the door actuator or its relay, which CARB requires for outputs. Mitsubishi's Outlander PHEV from 2023 switches the door opener relay from the engine module and sets P04BF in refuelling mode if the door sensor still reports closed 1 s after actuation. Mitsubishi shows a 'refuelling system service required' message for these codes and gives no drive-cycle pattern.

Likely causes

Open control wire or connector at the door actuator
Actuator motor or solenoid open internally
Actuator supply, fuse or relay not working
Driver in the module

Symptoms

  • Filler door does not open or lock as commanded
  • Refuelling system message in the instrument cluster
  • Possibly check engine light

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–350
Time0.5–2 h

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

Parts involved

fuel fill door unlock actuatorfuel door opener relayactuator wiringengine control module

Related codes

P04BBP04C0P04C1P04C2P04B5P04B6

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