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). P04BB concerns the lock circuit: the module detects an open circuit in the output to the door actuator or its relay, which CARB requires for outputs. A separate lock output exists only on actuators that drive actively in both directions; spring-return actuators have only the unlock circuit. 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 open or lock as commanded
- Refuelling system message in the instrument cluster
- Possibly check engine light
Most likely causes
- Open control wire or connector at the door actuator
- Actuator motor or solenoid open internally
- Actuator supply, fuse or relay not working
- Driver in the 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 P04BB means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 4: Emissions
- BB: Specific fault in that system
Frequently asked questions
Can I keep driving with code P04BB?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P04BB?
The most common causes are: open control wire or connector at the door actuator; actuator motor or solenoid open internally; actuator supply, fuse or relay not working.
Related codes
- P04BFFuel Fill Door Unlock Control Circuit/Open
- P04BCFuel Fill Door Lock Control Range/Performance
- P04BDFuel Fill Door Lock Control Circuit Low
- P04BEFuel Fill Door Lock Control Circuit High
- P04B5Fuel Fill Door Stuck Open
- P04B6Fuel Fill Door Stuck Closed
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.