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.
Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
Symptoms
- Filler door does not unlock or lock reliably
- Refuelling system message
- Possibly check engine light
Most likely causes
- Actuator does not travel fully (blocked or worn)
- Switch in the actuator worn or misadjusted
- Door distorted, latch does not engage
- Module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P04C4 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 4: Emissions
- C4: Specific fault in that system
Frequently asked questions
Can I keep driving with code P04C4?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P04C4?
The most common causes are: actuator does not travel fully (blocked or worn); switch in the actuator worn or misadjusted; door distorted, latch does not engage.
Related codes
- P04C3Fuel Fill Door Lock Position Sensor/Switch Circuit
- P04C5Fuel Fill Door Lock Position Sensor/Switch Circuit Low
- P04C6Fuel Fill Door Lock Position Sensor/Switch Circuit High
- P04C7Fuel Fill Door Lock Position Sensor/Switch Circuit Intermittent/Erratic
- P04B8Fuel Fill Door Position Sensor/Switch Circuit
- P04BCFuel Fill Door Lock Control Range/Performance
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.