P04BA
Fuel Fill Door Position Sensor/Switch Circuit High.
- 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
- BA
- FaultThe specific fault in that area
What it means
P04BA means the control unit has seen a voltage that is too high on the fuel fill door position sensor or switch circuit. The signal is above the expected range, which usually points to an open circuit, a short to voltage, or a faulty switch or sensor. On vehicles that use this input for the fuel system or evaporative emission control, the control unit may not be able to tell whether the door is open or closed. How the circuit is wired and used varies by model.
Symptoms
- Malfunction indicator lamp on
- Fuel filler door will not open or release, or does not register as open or closed (model dependent)
- Fuel gauge or refuelling status behaving oddly (model dependent)
- Evap system readiness monitor not completing
- Difficulty refuelling, or fuel pump nozzle clicking off early, if the evap system cannot vent for refuelling (model dependent)
- No noticeable driveability change in many cases
Possible causes
- Faulty fuel fill door position switch or sensor (internal open circuit or stuck output)likely
- Damaged, corroded or loose wiring or connector at the filler door switch, often from water ingress at the filler arealikely
- Open circuit in the signal or ground wire, giving a high voltage readinglikely
- Signal wire shorted to a voltage supplypossible
- Door latch or actuator assembly damaged, or the door misaligned so the switch does not operate correctlypossible
- Fault in the control unit that reads the switch (body or powertrain module, model dependent)rare
- Outdated control unit software where the manufacturer has issued a known fix for this coderare
How to diagnose
- Read all stored and pending codes and the freeze frame data, and note any other evap, fuel level or body control codes.
- Check for manufacturer service bulletins and software updates for the specific model and engine.
- Operate the filler door several times and watch the live data for the door status, checking that it changes between open and closed.
- Inspect the filler door, latch, switch and surrounding area for damage, dirt, corrosion, water ingress or misalignment.
- Inspect the wiring and connector between the switch and the control unit for chafing, broken pins, corrosion and pushed-out terminals.
- Using the wiring diagram, check the switch supply, signal and ground for continuity, and check for a short to voltage.
- Test the switch or sensor with a multimeter in both the open and closed positions against the specification for that model.
- If the wiring and switch are good, check the control unit supply and ground, and only then consider the control unit.
How to fix
- Replace the faulty fuel fill door switch or sensor.
- Repair or replace damaged wiring, and clean or replace corroded connectors and terminals.
- Repair any short to voltage or open circuit found in the signal or ground wire.
- Repair or adjust the filler door latch or actuator so the switch operates correctly.
- Update the control unit software if a known fault is documented for this code, or repair or replace the control unit if it is confirmed faulty.
Can I keep driving?
The car can normally be driven as usual, as this fault rarely affects safety or engine running. Book it in soon, as the warning lamp will stay on and the evap system may not complete its self-tests, so you could fail an emissions test or have trouble refuelling.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.