What does it mean?
Here the module reads the fuel filler door position circuit and finds the voltage above its upper valid limit. In a switched circuit that usually means the return path is missing, so the signal line floats at the reference level and never gets pulled down, or an external voltage source is feeding the line. Practically that translates into an open wire, a disconnected or corroded connector, a switch that no longer closes, or a short to battery voltage in the loom. Because a plausible door state cannot be established, refuelling control and any evaporative test that requires a known door position are put on hold. Diagnosis is straightforward with a meter, as long as the switch itself is verified separately from the wiring.
Symptoms
- MIL (check engine lamp) on with a fuel filler door circuit code stored
- Live data shows the door as open at all times, even when it is closed
- Fuel filler door will not lock or the vehicle reports it as open
- Evaporative monitors that never complete, causing an emissions test failure
- Warning message about the fuel filler door on equipped vehicles
Likely causes
- Open signal or ground wire between the module and the fuel filler door switch
- Switch contacts that no longer close due to wear, corrosion or internal breakage
- Corroded, burned or backed out terminal in the switch connector
- Connector left unplugged or only partly latched after body or trim work
- Signal wire shorted to a battery voltage feed in the same harness bundle
- Corroded body ground point serving the switch circuit
- Module input failure, only once the external circuit has tested good
How to fix it
- Watch the door status in live data while cycling the door to confirm the input never changes
- Unplug the switch and jumper the signal to ground at the harness connector; if the status changes, the wiring is intact and the switch is at fault
- Measure across the switch terminals with the plunger pressed, checking that it actually closes the circuit
- Test the signal wire for continuity to the module and check the switch ground for a good connection with a voltage drop test
- With the switch unplugged, look for unexpected battery voltage on the signal wire, which would indicate a short to power
- Inspect the connector and grommet area for corrosion, water, damaged locks and pushed out terminals
- Repair the open or short, or replace the switch, then clear the code and verify the status follows the door reliably