P04C5: Fuel Fill Door Lock Position Sensor Circuit Low

What it means

Same as P04C3 with the signal voltage below the plausible range. 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 lock-position sensor sends the module a signal showing whether the lock is engaged or released. P04C5 sets when that signal falls below the expected electrical range, such as when the signal wire is shorted to ground.

Common causes

Most likely first.

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

Symptoms

• Lock status may be unavailable or incorrect
• Fuel-fill door may not lock or unlock as expected

How to diagnose it

1. Check freeze-frame data and scan-tool lock-position feedback to confirm whether the low reading is present when the lock state is monitored.
2. Inspect the sensor connector and harness for chafing, moisture, corrosion, or a pin pushed back into the connector.
3. Gently move the harness while watching the scan-tool reading to see whether the low signal changes.
4. Using the wiring diagram, test the sensor signal wire for a short to ground and check its connections according to the manufacturer's procedure.
5. If the wiring checks out, test the position sensor and module input against the manufacturer's specification.

Common fixes

• Clean and secure a loose or corroded sensor connector.
• Repair chafed signal-wire insulation that is contacting ground.
• Replace a damaged connector terminal or seal.
• Replace the position sensor or repair the module only if testing isolates the fault to that part.

Can I keep driving?

You can generally drive if the fuel-fill door is closed, but the module may not know whether the lock has engaged or released. Check that the door is secure and address the fault if it will not lock properly.