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

On plug-in hybrids with a sealed, pressurised tank, pressing the fuel button (open request) starts a refuelling mode: the module opens the tank valve, releases the pressure into the charcoal canister and only then unlocks the filler door via an electric actuator (Ford patent). P04CA means the button line is below its valid range. Ford's Escape and Corsair 2.5 (2020–26) set it with an open supply circuit to the button, so the door does not open. With buttons that pull to ground (Mitsubishi), a permanently low line appears as stuck on (P04CD) instead.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

Fuel button has no effect, door does not open
Refuelling system message in the instrument cluster
Refuelling only via emergency release

Most likely causes

Button supply circuit open (Ford: supply circuit or splice)
Button line shorted to ground
Fuel button faulty
Module

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
Check the continuity of the wire between the component and the control module.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: easy
It affects emissions.

What each character of P04CA means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
CA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P04CA?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P04CA?

The most common causes are: button supply circuit open (Ford: supply circuit or splice); button line shorted to ground; fuel button faulty.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.