P0457: EVAP System Leak Detected (Fuel Cap Loose/Off)

What is P0457?

The trouble code P0457 means “Evaporative Emission System Leak Detected (Fuel Cap Loose/Off.”) The DTC (Diagnostic Trouble Code) P0457 occurs when your powertrain control module (PCM) detects a large leak within the EVAP system. 

Your vehicle’s EVAP System (Evaporative Emission System) comprises many critical components, including the following:

• Fuel tank
• Gas cap or fuel cap
• EVAP pressure sensor
• Charcoal canister
• Purge valve
• Vent valve
• Vacuum hose 

When you turn off your vehicle, the powertrain control module shuts the vent valve and canister purge valve, trapping harmful fuel vapor in your engine. On restarting your vehicle, the control module opens the purge valve and charcoal canister, drawing the fuel vapor via the vacuum hose into the intake manifold, to be burned in the engine. 

The powertrain control module monitors the EVAP system to ensures no vacuum leak. If the control module detects a large leak, it’ll turn on the Check Engine Light and log trouble code P0457. 

Here are the other engine codes related to the Evaporative Emission Control System:

• P0450: EVAP System Pressure Sensor Malfunction
• P0451: Evaporative Emission Control System Pressure Sensor Range
• P0452: Evaporative Emission Control System Pressure Sensor Low Input
• P0453: Evaporative Emission Control Pressure Sensor High Input
• P0454: Evaporative Emission Control System Pressure Sensor Intermittent
• P0455: System Gross Leak Evaporative Emission
• P0456: Evaporative Emissions System Small Leak Detected
• P0458: EVAP System Purge Valve Circuit Low
• P0459: Evaporative Emissions System Purge Control Valve Circuit High

Common symptoms

Here are some noticeable symptoms commonly associated with the trouble code P0457: 

1. A Flashing Check Engine Light

The key function of the EVAP system is to prevent harmful fuel vapor from escaping into the atmosphere. 

If the engine control module detects an EVAP system leak or fault in the EVAP vacuum system, it’ll turn on the Check Engine Light on your dashboard and log error code P0457. However, a lit Engine Light can also signify other trouble codes, so, a full diagnosis is the best way to identify the root cause. 

2. The Smell Of Fuel Vapor

The smell of fuel vapor in your vehicle could signify error code P0457. 

In most cases, the fuel vapor smell occurs due to a faulty or loose gas cap. However, it could also occur due to a faulty EVAP canister, EVAP vacuum hose, EVAP pressure sensor, or purge valve.

3. A Spike In Fuel Consumption

When the purge valve is faulty, the fuel vapor stored in the EVAP canister escapes into the environment instead of getting burned as fuel inside the combustion chamber. 

As a result, your vehicle will consume more fuel than usual, and you’ll notice the fuel level declining rapidly — a common sign associated with DTC P0457.

Can I still drive?

While trouble code P0457 may not cause any immediate drivability issues, it can severely damage your engine and EVAP system if left unresolved. 

P0457 indicates the largest vacuum leak among all the leak-related EVAP codes (P0455, P0456, P0457), and will cause your vehicle to fail the emissions test as required by law. 

So, if you notice the Check Engine Light illuminated, you should have your vehicle inspected at a repair shop soon.

P0457 causes

Most often, the cause of the trouble code P0457 is a loose gas cap. Here are some other common triggers: 

• Damaged gas or fuel filler cap
• A leak in the vacuum hose or gas tank
• Cracks in the carbon canister 
• Faulty purge valve or vent control valve

Diagnosis

To identify the problem, code P0457 requires a complete diagnosis of the EVAP system. 

Here’s an overview of how a skilled technician would diagnose the issue:

1. Your mechanic will first check for signs of a loose gas cap and tighten it if required. Then, using an OBD2 scan tool, they’ll verify and clear the existing EVAP code and see if the Check Engine Light or the EVAP code resurfaces. 
2. Next, they’ll visually inspect the gas cap, fuel tank, charcoal canister, and EVAP hose for visible cracks or damage. 
3. The mechanic will continue to check the rest of the EVAP Control System, including the purge volume control valve (usually under the intake manifold.)
4. Finally, your mechanic will use a smoke machine to conduct a smoke test, which is extremely useful in detecting an EVAP leak that’s not visible to the eyes. 

Possible repairs for P0457 & Costs

Depending on the diagnostic results and vehicle type, there are many potential solutions for the EVAP code P0457. 

Here are some common fixes for a problematic Evaporative Emission Control System: 

• Prevent fuel vapor leak by tightening or replacing the faulty gas cap
• Repair or replace the EVAP system vacuum hose (also known as the emission hose)
• Replace a defective charcoal canister
• Inspect and repair faulty fuel lines
• Seal cracks in the intake manifold

Repair costs

Here are the average estimated costs for fixing the EVAP code P0457, including labor: 

• Fuel cap: $20 to $ 60
• EVAP system purge control valve: $150 to $200
• EVAP canister: $200 to $600
• EVAP vent control valve: $150 to $200
• Fuel tank pressure sensor: $250 to $350