What does it mean?
This is a generic powertrain code, meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.
Diagnostic Trouble Code (DTC) P0457 relates to a vacuum leak in the Evaporative Emission system used to prevent fuel vapor leaks into the atmosphere. P0456 and P0455 are similar codes referring to the degree of vacuum leak from smallest to largest. The fix is similar in all cases.
This code does not cause driveability issues but should be fixed as soon as possible. It indicates a vacuum leak is present that compromises the operation of the Evaporative Emission system.
Automobiles require two types of emission controls – passive and active. The active part involves controlling the fuel ratio and the catalytic converter’s ability to convert carbon monoxide, nitrogen oxides, and hydrocarbons into harmless water and carbon dioxide.
The passive part relates to this P0457 code. Fuel vapor accounts for 20% of harmful evaporative emissions. To prevent these vapors from entering the atmosphere, they are contained in the fuel system and drawn into the engine via the intake manifold.
The Evaporative Emission system consists of the fuel tank, a vent line to the charcoal canister to contain fuel vapors, a pressure sensor on the fuel tank, a purge valve on the charcoal canister, a vent line to the fill neck shut-off valve, and a purge line from the charcoal canister purge valve to the intake manifold.
When the engine is off, the vent shut-off valve and the tank purge valve are closed. Fuel cannot escape into the atmosphere. When the engine starts, the purge valve on the tank opens to allow trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time, the vent shut-off valve also opens to allow a small amount of air into the tank to mix with the fuel vapor for a better mixture. Once purged and the pressure sensor in the tank shows a significant drop, both valves close again, sealing the system.
There is a major leak preventing the system from being drawn into the vacuum needed to pull fuel vapors into the engine to burn.
Related Evaporative Emission fault codes include P0450, P0451, P0452, P0453, P0454, P0455, P0456, P0458, and P0459.
Symptoms
Symptoms of a P0457 code vary depending on the component or system causing the fuel seal disruption. Not all will be present at once.
Illumination of the Malfunction Indicator Lamp (MIL) with P0457 DTC set
There may be an occasional fuel smell
Fuel economy is affected when fuel can evaporate into the atmosphere
Potential Causes
Causes
of this DTC may include:
This code relates to a major leak. The most common cause is the gas cap. Either it was left loose, or it is cracked, missing, or has a foreign object or dirt on the threads preventing a proper seal.
If the gas cap is not the cause, a hose may have rotted and cracked or perhaps come loose. The system is not under any abuse, so age and weather conditions may be to blame.
The vacuum canister may have cracked
Diagnostic and Repair Procedures
Always go online and check for any TSBs (Technical Service Bulletins) related to your vehicle and this code.
The emission system on most vehicles is covered by warranty for an extended period, 80 to 100,000 miles. The reasoning relates to the fact that without causing driveability issues, many owners will neglect to repair such a problem.
Inspect the gas cap. Look for dirt on the threads, cracks, and general condition. Install it and ensure it clicks into place. If the gas cap was to blame, the Check Engine Light may be reset with a simple code scanner, or the code will reset after three drive cycles where the computer no longer sees the issue.
Raise the vehicle and inspect all vacuum hoses. Replace any that are cracked or have lost flexibility and will no longer create a tight fit on the port.
Check the fitting on the intake manifold for cracks at the point where the emission hose connects.
Check the charcoal canister for cracks.
Place a vacuum pump on the emission hose (engine side) and pump to about 10 inches of vacuum. If there is no leak, the vacuum will hold its position. If it drops, a leak is present between the engine and the canister purge valve.