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P0457
P0457 (generic OBD-II): EVAP leak from a loose or missing fuel cap
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Low
Quick answer
The EVAP test could not pull vacuum right after refuelling, which points to a loose or missing cap. Close it until it feels firm and drive for a few days without clearing the code.
Safety first
Stop and check this first
- Refuelling with the engine off and always closing the cap until firm stops P0457 coming back through a simple slip.
Safe checks you can perform
- Cap closure
- Cap seal and filler neck
- Follow-up with the reader
Leave these tasks to a qualified professional
- Do not attempt this professional task: Cap and EVAP sealing test
- Do not attempt this professional task: Completed EVAP monitor
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Cap and EVAP sealing test
What they doIf the code returns with the cap properly closed, the technician tests the cap and fills the system with smoke to find the leak.
They must show youthe cap test result and the leak point found with smoke.
In writingwhether the cap or another part is replaced, its number and the reason.
Completed EVAP monitor
What they doThe technician confirms with the scan tool that the EVAP monitor has completed after the fix and no code is pending.
They must show youthe EVAP monitor as complete and a code list with no leak codes.
In writingthe date and mileage of the check.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Cap closure
- Who:
- you, with the engine off.
- How:
- open and reclose the cap until it clicks or feels firm, making sure it is not cross-threaded.
- Result that matters:
- whether the cap was loose or badly fitted.
- If it was loose:
- close it properly; Nissan says the light goes off after a few trips if there is no other fault.
- If it was closed properly:
- check the seal in the next step.
- Evidence to keep:
- the date and mileage of the refuel and of the cap check.
No flames or cigarettes near the filler neck.
Evidence: Nissan USA malfunction indicator light guide · Ford 2020-2023 gasoline OBD system operation
Cap seal and filler neck
- Who:
- you, with the engine off.
- How:
- look at the cap's rubber seal and the edge of the filler neck for cuts, dirt or dents.
- Result that matters:
- whether the seal or neck is damaged.
- If there is damage:
- the cap cannot seal; show the photo at the workshop or parts counter.
- If everything looks fine:
- if the code returns, the leak is elsewhere in the system.
- Evidence to keep:
- a photo of the seal and the filler neck.
Evidence: Nissan USA malfunction indicator light guide
Follow-up with the reader
- Who:
- you, with a generic OBD-II reader and the car parked.
- How:
- without clearing, check over the following days whether the EVAP monitor completes and whether P0457 stays active or P0455 appears.
- Result that matters:
- whether the code goes away or turns into another leak code.
- If the monitor completes with no code:
- this confirms it was the cap.
- If P0457 returns or P0455 appears:
- the leak is not just the cap; workshop smoke test.
- Evidence to keep:
- dated captures of the monitor status and codes.
Do not look at the reader while driving.
Evidence: Ford 2020-2023 gasoline OBD system operation
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Vehicles
- Brand
- OBD-II genérico
- Product type
- Cars
Known code variants
- P0457
- P0457 fuel cap loose
- P0457 OBD2
- P0457 tapón gasolina suelto
What it means
P0457 is the generic code for an EVAP leak detected with the fuel cap loose or off. In Ford's OBD summary it is the same large leak check as P0455, but failing after a refuelling event, which is why it is put down to the cap. Nissan also says to check the cap when the engine light stays on steady. The code does not guarantee it: a split line near the filler neck or an open valve would give the same result if it coincides with refuelling.
Warnings and stop conditions
- Loweditorial warning
Refuelling with the engine off and always closing the cap until firm stops P0457 coming back through a simple slip.
Evidence: Nissan USA malfunction indicator light guide · Ford 2020-2023 gasoline OBD system operation
Symptoms and causes
Probable causes · in order
- Cap not fully closedCommon
Most common after refuelling. It is confirmed when, with the cap properly closed, the monitor completes and the code does not return.
Evidence: Nissan USA malfunction indicator light guide · Ford 2020-2023 gasoline OBD system operation
- Damaged seal or capPossible
A closed cap with a broken seal does not seal. It shows when you inspect the rubber and when the code returns with the cap tight.
Evidence: Nissan USA malfunction indicator light guide
- Large leak elsewherePossible
If the code returns with a good cap, the leak may be in lines or valves, as with P0455.
Evidence: Ford 2020-2023 gasoline OBD system operation
Virtual technician
Does P0457 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Nissan USA malfunction indicator light guide
Nissan USA · official_doc
- 2
Ford 2020-2023 gasoline OBD system operation
Ford Motor Company · 2023 · manual
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