P0457 EVAP Leak: Gas Cap Loose or Off
Drive normally - check soon
The computer found a large fuel vapor leak right after a fill-up, and it blames the gas cap. Tighten the cap until it clicks or replace a worn one. The car drives the same.
- Safe to drive?
- Yes
- Typical cost at a shop
- $61-$150 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 1 note with links
Check if the gas cap fixed it: clear the code and watch the EVAP readiness monitor.
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What it means
Your fuel system is sealed so fuel vapor is stored and burned instead of escaping. P0457 means the computer found a large leak and, because the fuel level just went up, it concluded the gas cap was left loose or off after refueling.
The technical version
Many cars set P0457 instead of a general leak code when the EVAP leak test fails soon after the fuel level rises, which points to the filler cap. The test closes the vent valve and tries to hold a vacuum or pressure on the tank; with a loose cap, nothing holds. If the cap is fine, the same diagnosis as a large leak applies (P0455).
Official name: Evaporative Emission System Leak Detected (Fuel Cap Loose/Off).
Symptoms
- The check engine light, often with a check fuel cap message.
- Sometimes a fuel smell near the filler.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A gas cap left loose or off | most common | It came on right after a fill-up. |
| A worn gas cap seal | common | The rubber seal is flat, cracked or torn. |
| A damaged filler neck or capless filler flap | less common | Rust or damage where the cap or nozzle seals. |
| A large leak elsewhere in the EVAP system | rare | A new cap does not help; P0455 may appear. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
There is no single live reading that proves this fault. The useful ones are fuel tank pressure (where fitted) and EVAP purge percentage. The real check is the EVAP readiness monitor: after a fix, it should show complete within a few days of normal driving, and the code should not return.
What to check first, in order
-
Tighten the gas cap until it clicks, or refit it if it was left off.
It is the usual cause.
What the data shows: No reading needed.
Cost: free
-
Look at the cap seal and the filler neck.
A worn seal cannot hold the test.
What the data shows: No reading needed.
Cost: $138-$150 at a shop (Gas cap replacement, RepairPal)
-
Clear the code and drive a few days.
The EVAP test needs time to run.
What the data shows: EVAP readiness changes to complete.
Cost: no cost if you have a scanner
-
If it returns with a good cap, have a smoke test done.
The leak is somewhere else.
What the data shows: Not a scanner step.
Cost: $61-$90 at a shop (Emission system diagnosis (shop), RepairPal)
Is it safe to drive?
Drive normally - check soon
Yes. It is a fuel vapor fault, not a fuel leak.
Harmless to drive with. You lose some fuel vapor, may smell fuel, and will fail an emissions test until the light goes out. Many cars also show a separate check fuel cap message.
Stop driving and get help if
- You see liquid fuel dripping or smell strong fuel inside the car.
What it costs
| Repair | Typical cost |
|---|---|
| Emission system diagnosis (shop)RepairPal, updated September 3, 2026 | $61-$90 |
| Gas cap replacementRepairPal, updated September 3, 2026 | $138-$150 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner.
Can I clear it? Will it come back?
Many cars turn the light off by themselves after the EVAP test passes on later drives, which can take several days. Clearing the code with a scanner turns it off at once, but the EVAP monitor still has to complete before an emissions test.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
Infiniti 2012 and newer
Infiniti bulletin EC13-015h (November 2020) says a loose fuel filler cap may be the cause of EVAP leak codes. Check the cap first.
Infiniti EC13-015h via NHTSA static.nhtsa.gov
Related codes
How Obie handles P0457
Obie reads the EVAP codes and readiness, tells you what to check first, and tracks whether the EVAP monitor completes on later drives. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Will P0457 clear by itself?
Often, after the cap is tightened and the EVAP test passes on later drives. That can take several days.
Do I need a new gas cap for P0457?
Only if the seal is worn or the cap does not click. Try tightening it first.
Is P0457 serious?
No. It does not affect how the car runs, but it fails emissions tests.
Sources
- RepairPal: P0457 code page repairpal.com
- RepairPal: Emission system diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Gas cap replacement (updated September 3, 2026) repairpal.com
- Infiniti EC13-015h via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0457 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.