The leak test points to a loose or missing fuel cap. The driver usually sees only the engine light after refuelling.
Likely causes, most common first
- Fuel cap not tightened
- Missing or wrong fuel cap
- Worn cap seal
- Dirty or damaged filler neck
Parts usually involved
- Fuel cap
- Filler neck
Test before you replace
Tighten or test the cap, inspect the filler neck, clear the code and confirm with a drive cycle.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.