P04C2 code meaning
Fuel Fill Door Unlock Control Circuit High
Powertrain system Generic code P04xx codes Check engine light
What P04C2 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). P04C2 concerns the unlock circuit: the voltage in the control circuit is above the expected range – typically a short to positive, or with a low-side driver an open load circuit. Mitsubishi's Outlander PHEV from 2023 checks it with the power on, not only in refuelling mode. Mitsubishi shows a 'refuelling system service required' message for these codes and gives no drive-cycle pattern.
P04C2 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 P04C2
- Filler door does not open or lock as commanded
- Refuelling system message in the instrument cluster
- Possibly check engine light
Common causes of P04C2
- Most likelyControl line shorted to battery voltage
- PossibleActuator load circuit open (seen as high with a low-side driver)
- PossibleRelay sticking or faulty
- Less likelyModule 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 P04C2 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). |
| C2 | The exact fault in that area. |
What to do next
- Note P04C2 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 P04C2
What does P04C2 mean?
P04C2 means "Fuel Fill Door Unlock Control Circuit High". 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 P04C2?
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 P04C2 fail an emissions test?
Yes, it can. P04C2 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 P04C2 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P04C2 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.