P04C4 code meaning
Fuel Fill Door Lock Position Sensor/Switch Circuit Range/Performance
Powertrain system Generic code P04xx codes Check engine light
What P04C4 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). The lock position sensor in the actuator reports locked or unlocked – not to be confused with the door position sensor (open or closed, P04B7–P04BA). P04C4 means its feedback is electrically valid but does not fit the commanded state – for example unlock commanded and the sensor still reports locked – or does not change. 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.
P04C4 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 P04C4
- Filler door does not unlock or lock reliably
- Refuelling system message
- Possibly check engine light
Common causes of P04C4
- Most likelyActuator does not travel fully (blocked or worn)
- PossibleSwitch in the actuator worn or misadjusted
- PossibleDoor distorted, latch does not engage
- Less likelyModule
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel fill door lock position switchFuel fill door lock actuatorSensor wiringEngine control module
What each part of P04C4 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). |
| C4 | The exact fault in that area. |
What to do next
- Note P04C4 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 P04C4
What does P04C4 mean?
P04C4 means "Fuel Fill Door Lock Position Sensor/Switch Circuit Range/Performance". 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 P04C4?
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 P04C4 fail an emissions test?
Yes, it can. P04C4 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 P04C4 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P04C4 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.