P04CBFuel Fill Door Open Request Sensor/Switch Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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). P04CB means the button line is above its valid range. On Mitsubishi's Outlander PHEV from 2023 the engine module feeds the button and a press pulls the line to ground; P04CB sets if the line carries battery voltage for 2 s, i.e. a short to positive. Mitsubishi shows a 'refuelling system service required' message for these codes and gives no drive-cycle pattern.
- What you may notice
- Fuel button has no effect, door does not open
- Refuelling system message in the instrument cluster
- Refuelling only via emergency release
- Likely causes
- LikelyButton line shorted to positive
- PossibleFuel button faulty
- PossibleConnector or wiring damaged
- RareModule
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.