EVAP System Leak Detected (Fuel Cap Loose/Off)
What it means
The engine computer has detected a leak in the EVAP system, usually after refueling, and suspects the fuel cap is loose or missing. This is one of the simplest codes to fix, and tightening the cap may be enough.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Check engine light on, or a fuel cap warning message on some vehicles.
- Light fuel smell near the filler.
- No driving symptoms.
- Failed emissions test.
Possible causes5
- Fuel cap not tightened after refueling.
- Fuel cap left behind at the gas station.
- Damaged or cracked cap seal.
- Wrong type of cap for the vehicle.
- Dirt or damage on the filler neck rim preventing a good seal.
How to diagnose5
- Make sure the cap is present and tighten it until it clicks.
- Inspect the cap seal for cracks or hardening.
- Inspect the filler neck rim for dirt, rust or damage.
- Confirm the cap meets the vehicle specification.
- If the code returns with a good cap, have a smoke test done.
How to fix5
- Tighten the fuel cap.
- Clean the filler neck rim.
- Replace the cap with a correct one if its seal is damaged.
- Repair the filler neck if its rim is damaged.
- Clear the code, or drive several days until it turns off after the self-test passes.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 40–400 (≈ USD 11–107)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
It often costs nothing beyond tightening the cap or buying a new one; the cost rises only if a smoke test or filler neck repair is needed.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
I tightened the cap. When will the light go off?
It usually goes off after several days of driving once the computer retests the system successfully, or it can be cleared right away with a scan tool.
Does this code affect the engine?
No. It does not noticeably affect performance or fuel economy, but fuel vapor escapes until the cap is sealed.
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