Open circuit or high resistance in the unlock control wiring or connector, causing the monitored voltage to read high; Faulty fuel filler door lock or unlock actuator, internally open or failed; Corroded, loose or water-damaged connector at the actuator or the control module; Control circuit shorted to a voltage supply; Faulty driver stage inside the controlling module (body control or powertrain, depending on model); Mechanical jam of the door or latch overloading the actuator and causing a circuit fault.

P04C2

Fuel Fill Door Unlock Control 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
C2: FaultThe specific fault in that area

What it means

P04C2 means the control module saw a higher voltage than expected on the circuit that drives the fuel filler door unlock function. The module commands the unlock output and monitors it, and the feedback did not match what it expected. The exact layout, including the actuator type and which module controls it, depends on the vehicle.

Symptoms

Fuel filler door will not open, or only opens with the manual release
Fuel filler door will not unlock when the fuel button or central locking is operated
Malfunction indicator lamp on, or a fuel filler door warning message on some models
Fuel filler door stays unlocked or does not latch
Difficulty refuelling, or a fuel filler door actuator that is silent when operated

Possible causes

Open circuit or high resistance in the unlock control wiring or connector, causing the monitored voltage to read highlikely
Faulty fuel filler door lock or unlock actuator, internally open or failedlikely
Corroded, loose or water-damaged connector at the actuator or the control modulepossible
Control circuit shorted to a voltage supplypossible
Faulty driver stage inside the controlling module (body control or powertrain, depending on model)rare
Mechanical jam of the door or latch overloading the actuator and causing a circuit faultrare

How to diagnose

Read all stored codes and freeze frame data, noting whether other body or central locking faults are present
Check that the fuel filler door and latch move freely and are not frozen, damaged or obstructed
Visually inspect the actuator, wiring and connectors for damage, corrosion, water ingress and chafing
Operate the unlock function and listen for the actuator, then use a scan tool's bi-directional test if the vehicle supports it
Check the wiring diagram for the model, then measure the supply, control and earth at the actuator connector with the unlock command active
Test the control wire for continuity and for a short to voltage, with the connectors disconnected
Test the actuator's resistance and operation using a fused, correctly rated supply, following the manufacturer's data
Clear the code, retest, and confirm it does not return before closing the job

How to fix

Repair or replace damaged wiring and fix any short to voltage or open circuit
Clean, repair or replace corroded or loose connectors and seal out moisture
Replace the faulty fuel filler door actuator or lock assembly
Free or repair a jammed or damaged filler door or latch mechanism
Replace or repair the controlling module only after wiring and actuator are proven good, with any coding it requires

Can I keep driving?

Low severity

The car can normally be driven as usual, as this fault does not affect engine running. Book it in soon, as you may struggle to refuel and may need to use the manual release.

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