Symptoms
- Check engine light on, often with no other symptoms
- Possible faint fuel smell
- No change in how the car drives
- Light may have appeared shortly after refueling
Likely causes
- CommonGas cap not tightened fullyMost caps need to be tightened until they click several times; a partial turn won't seal properly.
- CommonWorn or cracked gas cap sealThe rubber seal degrades over time and may not hold vacuum even when tightened.
- PossibleMissing gas capA cap left off after fueling immediately triggers an EVAP leak code.
- Less commonDamaged filler neck or cap threadsCross-threading or damage can prevent a proper seal even with a good cap.
What to do
- Check that the gas cap is present and tightened until it clicks (usually 3 clicks) rather than just snug.
- Inspect the cap's rubber seal for cracks, dirt, or damage.
- Replace the cap if it's damaged, doesn't click, or is missing.
- Clear the check engine light or simply keep driving; many systems clear it automatically after several successful drive cycles.
- Watch to see if the light returns after a few days of normal driving.
- See a shop if the light returns even with a good, tight cap, since that points to a different EVAP leak.
Tools and parts
Gas capSearch: “gas cap for [year make model]”
When to call a pro
This is a simple check most people can do themselves; see a shop only if the light persists after confirming the cap is good and tight.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.