Faulty fuel filler flap lock actuator (open-circuit motor or solenoid winding); Damaged, corroded or loose connector at the actuator, often wet from the filler area; Open circuit or broken wire in the harness between the control unit and actuator, especially at flexing points or the rear body area; Blown fuse or loss of power or ground supply to the lock circuit; Mechanical binding or ice or dirt in the flap mechanism causing actuator overload and damage; Fault within the controlling module (body control or central locking unit) output driver.

P04BB

Fuel Fill Door Lock Control Circuit/Open.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
BB: FaultThe specific fault in that area

What it means

P04BB is the generic code for a fault in the fuel fill door lock control circuit, specifically an open circuit. The control unit drives the fuel filler flap lock actuator and monitors the circuit. It set the code because it saw no current flow or an open-circuit condition on the control line when it commanded the lock or release.

Symptoms

Fuel filler flap will not open or will not lock
Fuel filler flap stuck shut after refuelling stop or central locking use
Fuel filler flap not locking when the car is locked
Warning lamp or message may show on some models
Flap operation works intermittently, depending on temperature or vibration

Possible causes

Faulty fuel filler flap lock actuator (open-circuit motor or solenoid winding)likely
Damaged, corroded or loose connector at the actuator, often wet from the filler arealikely
Open circuit or broken wire in the harness between the control unit and actuator, especially at flexing points or the rear body arealikely
Blown fuse or loss of power or ground supply to the lock circuitpossible
Mechanical binding or ice or dirt in the flap mechanism causing actuator overload and damagepossible
Fault within the controlling module (body control or central locking unit) output driverrare

How to diagnose

Read all stored codes and freeze frame data, note whether the fault is current or intermittent, and check for other body or locking codes
Test the flap operation by hand and with the central locking, listening for the actuator to click or whirr
Check the relevant fuse and the condition of the circuit's power and ground supplies using the wiring diagram for the specific model
Inspect the actuator connector and nearby harness for water ingress, corrosion, pin damage and chafing
Check the actuator for mechanical freedom, dirt, ice or a bent release mechanism
With the connector unplugged, measure the actuator winding resistance and compare with the model-specific specification
Check the control wire for continuity and for shorts to ground or supply between the module and actuator while commanding the lock using a suitable scan tool function
If wiring and actuator test good, check the controlling module's output signal and any applicable software updates for that model

How to fix

Replace the fuel filler flap lock actuator if its winding is open or it fails to operate
Clean, repair or replace corroded or damaged connectors and terminals, and seal against water ingress
Repair or replace the open or damaged section of wiring, following manufacturer repair guidance
Replace the blown fuse after finding and correcting the cause of the overload
Free, clean or repair the flap mechanism so the actuator is not under load
Replace or repair the controlling module only after all other causes have been ruled out, and apply any manufacturer calibration update if one is known to apply

Can I keep driving?

Low severity

The car is safe to keep driving, as this is a convenience and security fault rather than an engine or safety issue. Book it in soon, as the flap may become stuck shut and prevent refuelling, in which case use the manual release if the car has one.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.