Emission codes
P0457: evaporative emission leak, fuel cap loose or off
P0457 is the only OBD-II code that names a part you can fix in the parking lot. The computer saw the fuel vapor system open right after a refueling and concluded that the cap was not on properly.
P0457: can I drive, and what will the labor cost?
Estimated labor, replace the gas cap
$11 to $22
| Labor time (estimate) | 0.1 to 0.2 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| Low: fix when convenient Safe to drive; tighten or replace the cap and the light should turn off by itself after a few trips. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0457 is the generic OBD-II code for "evaporative emission system leak detected, fuel cap loose or off". Many vehicles monitor the fuel level and know when the tank has just been filled. If the vapor system test then finds a large leak, the computer infers that the cap was left loose, cross-threaded or off, stores P0457, and on some cars shows a "check fuel cap" message instead of, or before, the check engine light. The fix is usually to stop, check that the cap is present and clicks when tightened, and drive on. A cap with a worn or torn seal also sets it, and a new cap made for the car is cheap. Less often, the lip of the filler neck is dented or rusted so that no cap can seal. It is safe to drive. The light will go off by itself once the vapor test has passed on 3 consecutive trips, which can take several days because the test only runs in some conditions.
After the repair: when does the light go off?
Light off by itself after about
2 days
| Fault-free trips needed | 3 |
| Warm-up cycles before the code can be erased | 40 |
| Stored code gone after about | 40 days |
Federal rule for model years up to 2016 (40 CFR 86.1806-05); a misfire or fuel fault must also stay away under similar conditions. Clearing codes with a scanner also resets the readiness monitors an inspection checks.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0457 at a glance
| Code | P0457 |
| Standard description | Evaporative Emission System Leak Detected (Fuel Cap Loose/Off) |
| System | Evaporative emissions (EVAP) |
| Severity | Low: fix when convenient |
| Common symptoms | none, gas cap message on the dash |
Capless fillers
Some vehicles have no screw cap but a spring-loaded flap inside the filler. They can set the same code when the flap is held open by dirt or ice, or after a fill with an unusual nozzle. Opening and closing the flap a few times with the funnel supplied with the car, and cleaning around it, usually helps. The owner's manual describes the procedure.
Check the right things in the right order
- Is the cap there? It is easy to leave on the pump.
- Does it click? Turn until it clicks at least once.
- Is the seal intact, soft and seated? A crack or a flattened seal leaks.
- Is the lip of the filler neck smooth and round?
If all of those are fine and the code returns, the vapor system has a large leak that has nothing to do with refueling: read P0455 for the next steps, which include the purge valve and a smoke test.
Do not clear it before an inspection
Clearing the code with a scanner turns the light off, but it also resets the readiness monitors. An OBD inspection checks those too, and incomplete monitors are a failure, as the CARB fact sheet notes. It is better to let the car clear the light itself, or to drive for about a week after clearing before you go. Compare with P0456 for the very small leak case.
Likely causes of P0457, in order
| Cause | How often |
|---|---|
| Fuel cap loose, missing or cross-threaded | most frequent |
| Worn cap seal | most frequent |
| Damaged filler neck lip | less frequent |
P0457 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Replace the gas cap | 0.1 to 0.2 h | $11 to $22 |
| Replace the fuel filler neck | 1 to 2.5 h | $110 to $275 |