P04C1 code meaning
Fuel Fill Door Unlock Control Circuit Low
Powertrain system Generic code P04xx codes Check engine light
What P04C1 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). 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.
P04C1 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 P04C1
- Filler door does not open or lock as commanded
- Refuelling system message in the instrument cluster
- Possibly check engine light
Common causes of P04C1
- Most likelyControl line chafed against the body (short to ground)
- PossibleWater or corrosion at the connector
- PossibleActuator shorted internally
- Less likelyRelay or module driver faulty
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 P04C1 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). |
| C1 | The exact fault in that area. |
What to do next
- Note P04C1 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 P04C1
What does P04C1 mean?
P04C1 means "Fuel Fill Door Unlock Control Circuit Low". 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 P04C1?
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 P04C1 fail an emissions test?
Yes, it can. P04C1 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 P04C1 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P04C1 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.