Powertrain, generic · Auxiliary emission controls

P04C1 Fuel Fill Door Unlock Control Circuit Low

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). P04C1 concerns the unlock circuit: the voltage in the control circuit is below the expected range – typically the control line is shorted to ground. Mitsubishi's Outlander PHEV from 2023 uses an internal driver check in refuelling mode. Mitsubishi shows a 'refuelling system service required' message for these codes and gives no drive-cycle pattern.

Likely causes

Control line chafed against the body (short to ground)
Water or corrosion at the connector
Actuator shorted internally
Relay or module driver faulty

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

P04BDP04BFP04C0P04C2P04B5P04B6

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