Faulty fuel fill door lock position sensor or switch, worn or contaminated internally.; Damaged, corroded, or disconnected wiring or connector at the fuel door lock actuator or sensor.; Binding or mechanical obstruction in the fuel door lock mechanism, preventing full travel.; Failed fuel door lock actuator that no longer moves the lock or sends a correct position signal.; Water intrusion or debris in the fuel door area causing intermittent sensor operation.; PCM software issue or faulty PCM, though this is less common and should be diagnosed last.

DTC codes / P04xx · Auxiliary emission controls / P04C4

P04C4Fuel Fill Door Lock Position Sensor/Switch Circuit Range/Performance

P04C4 indicates that the powertrain control module (PCM) has detected an out-of-range or erratic signal from the fuel fill door lock position sensor or switch circuit. The computer expects a specific voltage or resistance pattern when the fuel door is locked or unlocked, and the observed value falls outside the valid range or does not change as expected.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

The fuel fill door may not lock or unlock properly, or the lock may cycle repeatedly.
A warning light on the dashboard, often the check engine light or a dedicated fuel door indicator.
The fuel door may appear closed but not be latched securely, leading to a loose door.
In some vehicles, a message on the driver information center stating the fuel door is ajar or has a fault.
Often no symptoms besides the warning light, especially if the door still latches mechanically.
Remote or central locking may not operate the fuel door, or may operate it intermittently.

Common causes, most likely first

Faulty fuel fill door lock position sensor or switch, worn or contaminated internally.
Damaged, corroded, or disconnected wiring or connector at the fuel door lock actuator or sensor.
Binding or mechanical obstruction in the fuel door lock mechanism, preventing full travel.
Failed fuel door lock actuator that no longer moves the lock or sends a correct position signal.
Water intrusion or debris in the fuel door area causing intermittent sensor operation.
PCM software issue or faulty PCM, though this is less common and should be diagnosed last.

How to diagnose and fix it

Inspect the fuel fill door lock mechanism for mechanical binding, debris, or damage, and clean or lubricate as needed.
Check the sensor or switch connector for corrosion, loose pins, or water intrusion, and repair the connection.
Measure the sensor or switch resistance or voltage while manually operating the fuel door lock, comparing to the manufacturer's specification.
Test the wiring harness between the sensor/switch and the PCM for continuity, shorts to ground, or shorts to power.
Replace the fuel fill door lock position sensor or switch if it fails the electrical test.
If the sensor and wiring are good, check the fuel door lock actuator operation and replace if it does not move or signal correctly.
Clear the diagnostic trouble code and verify the repair by cycling the fuel door lock and confirming the code does not return.

Before you replace the fuel door lock

A common cause of P04C4 is a simple mechanical bind in the fuel door lock linkage, which prevents the sensor from reaching its expected position and sets the code without any electrical fault.
The fuel fill door lock position sensor is often integrated into the lock actuator assembly, so a failed sensor may require replacing the entire actuator rather than a separate part.
Intermittent codes can be caused by water intrusion into the connector after car washes or rain, so always check for moisture and corrosion before condemning the sensor.
This code can be set by a weak or failing vehicle battery if voltage drops during locking, causing the PCM to see an out-of-range signal; verify battery health first.
Do not overlook the fuel door lock operation from the remote key fob or central locking system, as a fault in that circuit can mimic a sensor failure.

Can I keep driving with P04C4?

The vehicle is safe to drive with P04C4 because the fuel fill door lock is not a safety or emissions-critical system, but avoid forcing the fuel door closed if it is not latching properly. Have the fault diagnosed soon to prevent the door from opening unexpectedly while driving.

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.