P04BF code meaning
Fuel Fill Door Unlock Control Circuit/Open
Powertrain system Generic code P04xx codes Check engine light
What P04BF means
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.
P04BF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P04BF
- Filler door does not open or lock as commanded
- Refuelling system message in the instrument cluster
- Possibly check engine light
Common causes of P04BF
- Most likelyOpen control wire or connector at the door actuator
- PossibleActuator motor or solenoid open internally
- PossibleActuator supply, fuse or relay not working
- Less likelyDriver in the module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel fill door unlock actuatorFuel door opener relayActuator wiringEngine control module
What each part of P04BF means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| BF | The exact fault in that area. |
What to do next
- Note P04BF and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P04BF
What does P04BF mean?
P04BF means "Fuel Fill Door Unlock Control Circuit/Open". 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). It is a generic code, so it means the same on every make.
Is it safe to drive with P04BF?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P04BF fail an emissions test?
Yes, it can. P04BF is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P04BF to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P04BF clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.