P0457 – Evaporative Emission System Leak Detected (fuel cap loose/off)

The P0457 code is a sign you have a large leak in your EVAP system. It’s the big brother code of P0455 and P0456, which trigger when there are smaller leaks. Of the three, P0457 has the potential to be both the most serious, and the easiest to fix.

In the vast majority of cases, a P0457 code indicates a loose or missing gas cap. This is the first thing you should check if this code triggers. There are other ways your EVAP system could spring a large leak, however. Read on below to dig in deeper to this code and how you might be able to address it.

P0457 Code Definition

P0457 Code Definition (Generic): Evaporative Emission Control System (EVAP) Leak Detected

P0457 Dodge Code Definition: EVAP System – Loose Fuel Cap

P0457 Ford Code Definition: (EVAP) System Leak Detected (fuel cap loose/off)

P0457 Jeep Code Definition: EVAP System – Loose Fuel Cap

What Does P0457 Mean?

The evaporative emissions control (EVAP) system in your car limits the amount of fuel vapor that escapes from your tank into the atmosphere. The main offenders are hydrocarbons, which are the compounds that form smog. 

Everything from your fuel tank to your exhaust system is part of the EVAP control system. Individual components include the pressure sensor, charcoal canister, and vacuum hoses connecting them. The purge valve and vent control valve are on either side of the charcoal canister, regulating the flow of air in and out. 

The powertrain control module (PCM) or engine control module (ECM) communicates with the EVAP system to monitor its function. When a leak is detected, one of three codes can be triggered, depending on how serious the leak is. 

P0457 indicates a large leak in the EVAP system. While this is a generic powertrain code and applicable to all OBD2 vehicles, the exact size of leak that triggers P0457 (as opposed to P0455 or P0456) can vary. In any case, though, P0457 is the most severe of the EVAP leak codes.

A major leak in your EVAP system prevents it from forming a vacuum. This means fuel vapors won’t be pulled into the charcoal canister the way it should. They instead escape in the exhaust, which causes issues beyond simply increased emissions.

Though a large leak is a more significant engine problem, it can also be easier to find and fix. In many vehicles, P0457 triggers as a loose or missing gas cap. You’ll be looking for leaks on that size level, which will be easily visible to the naked eye. 

What Are The Symptoms Of The P0457 Code?

In some cases, you won’t experience any drivability issues with P0457. If there are symptoms, they often include:

What Are The Causes Of P0457?

  • Missing, loose, or damaged gas cap (most common)
  • Leaks or damage in vacuum hoses
  • Cracked or leaking carbon canister
  • Purge valve stuck or faulty
  • Vent control valve stuck or faulty

How Serious Is The P0457 Code?

The P0457 code is moderately serious. Even if you’re not experiencing drivability issues, you’re still wasting fuel when you drive with this code active. At the very least, you’ll need to repair it before your next emissions test. It can also lead to further issues with the air to fuel ratio, so while it’s safe to drive with this code active, you should fix the issue as soon as possible.

How To Diagnose And Fix The P0457 Code

P0457 code can be diagnosed by the digital multimeter
Using a digital multimeter can help diagnose the P0457 and other codes.

Tools you’ll need:

  1. Use an OBD2 scan tool to check for other trouble codes. You may see other trouble codes related to the EVAP system (P0450-P0459). If any other codes are present, fix those first. A P0440, P0455, or P0456 code along with P0457 suggests a more complex leak or a solenoid failure. 
  2. Inspect the gas cap. Check the threads for debris that could be preventing it from sealing fully. If you see any cracks, wear, or damage, replace your fuel cap. Make sure the new cap is an OEM (original equipment manufacturer) component. A misfitting gas cap can also trigger EVAP system leak trouble codes. 
  3. Visually inspect the hoses of the EVAP system. A leak of this size should be fairly easy to spot. Make sure you feel the undersides of hoses for hidden leaks. Also check the ends, verifying that there are no tears and that the connections are secure. 
  4. Clear the codes using an OBD2 scanner, then test drive your vehicle. If the P0457 code returns, use a vacuum pump to test the EVAP system. Pump it up to 10 inches of vacuum. If it holds a position, there is no leak in the system. A drop indicates you have a leaking valve or a leak in the charcoal canister itself. 
  5. Inspect the charcoal canister for cracks and damage. Replace if necessary. 
  6. Test the vent control valve and purge valve according to the steps outlined in your vehicle’s manual. This will typically involve applying voltage to the valve, then applying a vacuum to see if it holds. If the vacuum doesn’t hold, use a digital multimeter to test that the ground and power are providing the correct voltage. Replace any components that fail these tests.

Common Mistakes To Avoid While Diagnosing The P0457 Code

While a damaged or loose fuel cap is the most common cause of this trouble code, it can also be triggered by large leaks elsewhere in your system. Conduct a thorough diagnosis to be sure you’ve found the real root of the problem. 

Tips To Avoid P0457 In The Future

A loose, missing, or damaged gas cap is the primary cause of a P0457 code. Make sure you firmly replace your gas cap after each fill-up. This will prevent debris like rocks and dust from entering the threads.

The hoses and other components of the EVAP system are internal, meaning they’re not susceptible to external damage. You do have to prevent internal damage, however. Make sure they’re not touching any parts of the engine that could lead to leaks, either by puncturing or overheating the hoses.