Powertrain, generic · Auxiliary emission controls
P04C8 Fuel Fill Door Open Request Sensor/Switch Circuit
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
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). P04C8 is the general circuit fault of the fuel button input. 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.
Likely causes
Fuel button faulty
Wire or connector between button and module open or shorted
Button ground open
Module
Symptoms
- Fuel button has no effect, door does not open
- Refuelling system message in the instrument cluster
- Refuelling only via emergency release
Repair estimate
DifficultyEasyDIY possible
Parts and labour€20–200
Time0.3–1.5 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
fuel door open request switchswitch wiringengine control module
Related codes
References: law.cornell.edu, patents.google.com, mitsubishitechinfo.com.