P04C2: Fuel Fill Door Unlock Control Circuit High

What it means

Same as P04BE on the unlock side. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

How it works

The unlock-control circuit carries the module's command to the fuel-fill door actuator. P04C2 sets when the module detects that circuit at a higher electrical level than expected, which can happen if the control line is shorted to a supply source and the actuator does not receive a valid unlock command.

Common causes

Most likely first.

1. Control line shorted to supply
2. Connector pins corroded - high contact resistance
3. Supply wire pinched against B+ source

Symptoms

• Fuel-fill door may not unlock
• Fuel-fill door warning or status may be incorrect

How to diagnose it

1. Check freeze-frame data and scan-tool unlock command or status to identify whether the high reading occurs during an unlock request.
2. Inspect the unlock actuator connector and nearby harness for water, corrosion, pushed-back pins, chafing, or contact with a power wire.
3. Gently move the harness while monitoring the circuit status to see whether the reading changes.
4. Follow the wiring diagram to test for a short from the unlock-control line to a supply circuit, using the manufacturer's procedure.
5. If the harness and connector are sound, test the actuator and module output against the manufacturer's specification.

Common fixes

• Clean and secure a loose or corroded actuator connector.
• Repair a pinched or chafed unlock-control wire that contacts a supply circuit.
• Replace a damaged connector terminal or seal that is letting in water.
• Replace the actuator or repair the module only after testing identifies it as faulty.

Can I keep driving?

Driving is generally safe if the fuel-fill door is closed and secure, but it may not unlock when you need to refuel. Avoid forcing the latch, which can cause further damage.