Emission controls · Powertrain · generic (SAE-defined)
P0457: Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)
P0457 means the engine computer detected a leak in the evaporative emission (EVAP) system consistent with a fuel cap that is loose, missing, or not sealing.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0457 sets
Usually shortly after refueling, the powertrain control module (PCM) runs a leak test and finds the system cannot hold vacuum or pressure. Because the condition appeared right after a refueling event, many systems flag it specifically as a loose or missing cap. Test strategies are manufacturer-specific.
Common causes of P0457
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Fuel cap left loose or off after refueling
- Worn or damaged fuel cap seal
- Incorrect aftermarket fuel cap
- Damaged filler neck sealing surface
- On capless systems, a dirty or damaged flapper seal
P0457 symptoms
- Check engine light on
- Some vehicles show a check fuel cap or loose cap message
- Possible fuel odor
- No change in drivability
How P0457 is diagnosed
- Remove and reinstall the fuel cap until it clicks fully tight
- Inspect the cap seal for cracks, swelling, or missing pieces
- Inspect the filler neck lip for rust or damage
- On capless systems, check the flapper and seal for debris
- If the code returns, perform a smoke test to rule out other leaks
Typical fixes for P0457
- Tighten the fuel cap correctly
- Replace the fuel cap with the correct part
- Clean or replace a capless filler assembly
- Repair or replace a damaged filler neck
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Commonly used by GM, Chrysler, and Ford. Other manufacturers may report a loose cap as P0455 or P0442 instead.
Related codes & warning lights
P0457 FAQ
What does code P0457 mean?
P0457 means the engine computer detected a leak in the evaporative emission (EVAP) system consistent with a fuel cap that is loose, missing, or not sealing. The standard definition is "Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)."
Can I drive with a P0457 code?
Yes. Tighten or replace the fuel cap and continue driving normally. The light should turn off after several drive cycles if the cap was the cause.
How long until the light goes off after tightening the cap?
The computer needs to rerun its EVAP test, which can take a few days of normal driving including overnight cold soaks.
Can I clear P0457 myself?
You can clear it with a scan tool after fixing the cap, but the EVAP monitor will show incomplete until the test runs again, which may affect an emissions inspection.
Keep researching
More emission controls codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.