P04CA: Fuel Fill Door Open Request Sensor or Switch Circuit Low

What it means

Same as P04C8 with the signal voltage shorted to ground or constantly low. 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 fuel-fill door open-request switch sends a signal to the control module when pressed. P04CA sets when that input is held below its expected electrical range, often because the signal wire is shorted to ground or has a poor connection.

Common causes

Most likely first.

1. Signal shorted to ground
2. Connector pins corroded - high contact resistance
3. Harness chafing through insulation

Symptoms

• Fuel-fill door may release unexpectedly or fail to release
• Open-request button may not respond correctly

How to diagnose it

1. Check scan-tool live data for the open-request input and note whether it stays inactive or behaves incorrectly when the button is pressed.
2. Inspect the switch connector and harness for moisture, corrosion, pushed-back pins, or insulation worn through against ground.
3. With the circuit diagram, check the signal wire for a short to ground and inspect continuity through the switch and harness.
4. Wiggle the harness and connector while monitoring the input to reveal a fault that changes with movement.
5. If the wiring checks out, test the switch and module input against the manufacturer's specification.

Common fixes

• Dry and reconnect the switch connector; repair corroded or displaced terminals.
• Repair signal-wire insulation chafed through to ground.
• Replace the open-request switch if it pulls the input low when it should not.
• Repair a failed module input only after verifying the circuit and switch.

Can I keep driving?

If the door remains shut and secure, driving is generally possible, but check that it can be opened before refuelling. Because the input may be misread, the door could also release unexpectedly.