Car & driving · Free
P0457: EVAP leak – fuel cap loose or missing
P0457 is one of the easiest codes to fix: the car found a leak in its fuel vapor system and suspects the fuel cap. Tightening or replacing the cap usually solves it, and the light goes out on its own after a few drives.
- No account
- Runs on your device
- Phone & desktop
Check your car for P0457
Runs on your device
Connect your OBD2 adapter
- Plug the adapter into the OBD2 port – usually under the steering wheel, near the pedals.
- Switch the ignition on, or start the engine.
- Bluetooth adapter? Turn Bluetooth on. Nothing else to set up.
This browser cannot talk to OBD adapters. Use Chrome or Edge on Android, Windows or Mac – on iPhone, the free Bluefy browser works with Bluetooth LE adapters. The demo car works everywhere.
Classic Bluetooth adapter (PIN 1234)? Pair it in your system settings first, then choose USB or paired Bluetooth – on a computer or in Chrome 138+ on Android. Wi-Fi adapters cannot work in a browser.
Your car data stays on your device. The page talks to the adapter directly; codes, VIN and values are never uploaded.
Never use it while you drive. Set things up before you set off, or let a passenger handle the phone. Standard OBD2 reads engine and emissions data; ABS, airbag and coding need workshop equipment.
What P0457 means
Many cars notice when the tank has just been filled. If the fuel vapor system fails its leak test soon after, the most likely explanation is the cap that was just opened, so the computer stores P0457 instead of a general leak code. Some cars also show a Check fuel cap message on the dashboard.
The code says nothing about the engine. It only means that petrol vapor could escape from the tank, which is an emissions fault and a small loss of fuel.
Symptoms of P0457
- The check engine light, often a day or two after refuelling.
- A Check fuel cap or Tighten fuel cap message on some cars.
- A light petrol smell near the filler flap.
Causes of P0457, cheapest first
Work down the list in order: the first checks cost little or nothing, the last ones are jobs for a workshop.
The cap was not tightened
Turn it until it clicks at least once. Caps that hang on their strap are easily forgotten at the pump.
A worn or damaged cap seal
Check the rubber ring for cracks, flattening or dirt. A replacement cap made for your car is cheap; very cheap universal caps sometimes do not seal well.
A dirty or damaged filler neck
Sand, dirt or rust on the rim stop the seal from closing. Wipe the rim clean and look for dents.
A capless filler flap that does not close
Cars without a screw cap have a spring-loaded flap in the filler neck. Dirt or a damaged seal there has the same effect as a loose cap.
A leak elsewhere
If a good cap does not help, the leak is somewhere else in the system, and the next steps are the same as for P0455.
Can you drive with P0457?
Safe to drive. P0457 has no effect on the engine or on safety. Fix the cap at your next stop. If the code keeps returning with a new cap, have the vapor system tested before the next emissions inspection.
Check P0457 with OBD Studio
Connect your adapter above, or try the demo car, then:
- Tighten or replace the cap first.
- Then clear P0457 in Fault codes straight away, or let the car switch the light off itself after it has passed the leak test a few times.
- The Fuel vapour system (EVAP) monitor in Inspection shows when the car has finished its test.
- If P0457 or P0455 returns as a pending code, the cap was not the cause.
More fault code guides
Each of these codes has its own page with causes ranked by cost and the checks that go with them.
- P0420Catalyst efficiency below threshold
- P0171System too lean
- P0300Random or multiple misfire
- P0455EVAP system large leak
- P0442EVAP system small leak
- P0128Engine warms up too slowly
- P0172System too rich
- P0401EGR flow too low
- P0101Air flow sensor implausible
- P0135Front O2 sensor heater
- P0016Crankshaft and camshaft out of step
- P0011Intake camshaft timing over-advanced
- P0141Rear O2 sensor heater
- P0113Intake air temperature sensor high
- P0299Turbo underboost
- P0700Transmission control system fault
- P0087Fuel rail pressure too low
- P0562System voltage low
- U0100Lost communication with engine computer
More OBD Studio pages
Frequently asked questions
Will P0457 clear itself?
Yes, once the cap seals again. The car needs to pass its leak test, usually on a few drives over several days, before it switches the light off. You can also clear the code right after fixing the cap.
Do I need a new fuel cap for P0457?
Not always. First check that the cap was tight and clean. If its seal is cracked, flattened or brittle, a new cap made for your model is the cheapest repair.
Can I fail an inspection with P0457?
A stored code with the check engine light on usually fails an emissions inspection. Fix the cap, clear the code and drive for a few days so the EVAP self-test is complete before the appointment.
Can I read P0457 without going to a workshop?
Yes. With any ELM327-compatible Bluetooth LE or USB adapter, OBD Studio on this page reads P0457 and every other stored code for free, shows the freeze frame and clears the code after the repair. Nothing to install, no account.
