Need a P0457 diagnosis? Trust our experts.
Oops! We got lost!
Your location cannot be detected. Please enter your zipcode for nearby shops.
P0457 Severity
Once the vehicle's onboard system no longer detects the issue, most codes will disappear on their own. If your vehicle still has this code, however, it should be properly diagnosed to avoid a more serious problem.
For a proper diagnosis, RepairPal Certified shops have the equipment, tools, and expertise.
Moderate severity codes might not threaten the vehicle's safety or functionality immediately, but you should still get it diagnosed within a reasonable time frame to keep your car running well.
The evaporative control (EVAP) system captures any fuel vapors from the fuel tank and sends them through the vehicle's intake to be burned in the normal combustion process. When the engine control module detects a leak in this system, it will set code P0457.
RepairPal Car Genius™ is a free resource for vehicle owners seeking advice on maintenance, auto repair, shop inquiries, estimates, and finding a trustworthy repair shop in your area.
Call us at 877-913-1554
Available 9am – 6pm ET Monday through Friday
Code P0457 stands for Evaporative Emission System Leak Detected (Fuel Cap Loose/Off).
The evaporative emissions (EVAP) system is designed to prevent hydrocarbons (fuel vapors) from escaping into atmosphere. When hydrocarbons mix with sunlight and nitrogen oxides they form smog. To prevent this, the EVAP system stores the hydrocarbons in a canister. Then, when the time is right, the hydrocarbons are pulled into the engine and burned.
The main parts of the EVAP system are as follows:
Once the engine is shut down, the PCM closes off the EVAP system and checks for leaks. A leak at any part of the EVAP system, including the gas cap, can set a diagnostic trouble code. Code P0457 indicates the PCM has detected an EVAP leak, most likely caused by the gas cap.
EVAP system
Code P0457 is typically caused by one of the following:
Get it diagnosed by a professional
The first thing to check is the gas cap. Even if the cap seems secure, it may not be sealing properly. Gas caps are inexpensive, so if you have any doubt, replace the cap. Most of the time, this code is caused by gas cap issues.
Gas cap / Image source
Note: It may take a while for the check engine light to go out once the cap is replaced, since the EVAP system is not always monitored by the PCM. You can either drive the vehicle until the light goes out, which might take a very long time. Or you can turn it off with a diagnostic scan tool/code reader.
If the gas cap doesn’t do the trick, a visual inspection of the EVAP system should be performed. A trained eye can look for broken hoses or visibly damaged components. If a problem is found, the issue should be repaired and the code cleared. If nothing is discovered, the next step is to check for technical service bulletins (TSBs). TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.
Without the proper equipment, finding an EVAP leak can be extremely difficult. Technicians typically use smoke machines to pinpoint the problem, as outlined below.
Typically, a problem with the purge or vent valve will result in additional code being set, not just P0457. However, if no problems were found up to this point, it’s a good idea to test the valves. The EVAP system is not sealed unless the purge valve and vent valve are completely closed. A trained professional will test the valves by closing them and seeing if they hold vacuum.
The EVAP monitor is non-continuous. This means the system is only tested and monitored under certain conditions. For code P0457 to be set, the ignition must be off, the fuel must be at a certain level and ambient temperature must be within a pre-defined range.
