What does it mean?
This code narrows the fuel filler door position circuit fault to a specific electrical condition: the signal line is sitting below the module's lower voltage limit. Since the module normally expects the line to rest at a reference level and only be pulled down when the switch closes, a permanently low reading means something is holding the circuit at ground when it should not be. That is typically a wire shorted to the body, a wet or corroded connector bridging the pins, or a switch whose contacts have welded closed. The module cannot distinguish a genuine closed door from a shorted circuit, so it flags the reading as implausible and stores the code. Refuelling authorisation and the evaporative tests that need a valid door state are held back until the circuit is repaired.
Symptoms
- MIL (check engine lamp) on with a fuel filler door circuit code
- Live data shows the door as closed at all times, even with the door open
- Refuelling process not authorised or delayed on controlled filler systems
- Evaporative readiness monitors that will not complete
- Warning message about the fuel filler door on equipped vehicles
- Fault often appears first after washing the vehicle or driving in heavy rain
Likely causes
- Signal wire chafed to the body or a bracket, shorting to ground
- Water and corrosion inside the switch connector bridging the signal pin to the ground pin
- Switch contacts stuck closed by corrosion or mechanical wear
- Wiring pinched during previous body, tank or rear lamp work
- Damaged harness at the filler recess grommet where movement and moisture are common
- Internally shorted switch assembly
- Module input circuit failure, only after the wiring has been proven
How to fix it
- Confirm the fault is present, then unplug the switch and see whether the reading changes to the opposite state
- With the switch unplugged and the key off, measure resistance from the signal wire to ground; a very low value proves a wiring short
- Measure across the switch terminals with the plunger released; continuity when the switch should be open condemns the switch
- Inspect the connector for moisture, corrosion, damaged seals and pins that have been pushed together
- Follow the harness from the filler area back through the body grommet, checking for chafe and pinch damage
- Repair the short and seal the repair against water, or replace the switch as the measurements indicate
- Clear the code, cycle the door and confirm the status follows the door correctly in live data