Fix P0457: Mechanic’s solutions that WORKED

Code P0457: Gross leak in EVAP system pointing out a problem in your vehicle’s evaporative emission control system. Common causes include a loose or faulty gas cap, EVAP system leaks, malfunctioning EVAP purge solenoid, and even PCM problems.

P0457 quick overview

Meaning	P0457: Gross leak in EVAP system
Is it serious?	Should be addressed right away, one of the most serious codes for the EVAP system.
Possible causes	– Loose or faulty gas cap – Leaks in the EVAP system hoses, lines, or components – Malfunctioning EVAP purge solenoid – Faulty NVLD (Natural Vacuum Leak Detection) system components – Issues with the PCM (Powertrain Control Module)
How to diagnose?	1. Start by checking the gas cap. Ensure it’s securely tightened, and if it’s damaged or worn, consider replacing it. 2. Inspect the EVAP system for visible leaks, focusing on hoses, lines, and components. A smoke test can help identify hidden leaks. 3. Test the EVAP purge solenoid and the NVLD system for proper operation. Verify that the purge solenoid closes as commanded and that the NVLD system functions as expected. 4. If all other components appear to be in working order, consider checking for any PCM updates or, in rare cases, PCM replacement.
What is EVAP?	The EVAP system (Evaporative Emission Control System) captures and stores fuel vapors from the gas tank, preventing them from escaping into the atmosphere.

How to fix P0457 – learn from mechanics

I looked into P0457 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Subaru

Vehicle Information: 2002 Subaru Impreza WRX 2.0L

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Issue + Repair History:

• MIL activated with code P0457 indicating a gross evap leak.
• Smoke test revealed a leak at the purge valve when the purge valve solenoid was activated.
• Three vacuum lines associated with the purge valve: one to the intake, another to the intake manifold, and the last one to the purge valve solenoid.
• Previous repair: Gas cap was replaced.

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Other OBD2 Codes + Test Results:

• Code: P0457 – Gross evap leak
• Test results:
  • Solenoids tested and found to be operating normally.
  • Smoke test confirmed a leak at the purge valve.

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Suggestions from the Community:

1. With the key on, the purge valve should normally be closed; no smoke should escape. Recommended using a scan tool to close the back vent valve while performing the smoke test to close the system completely.
2. The DTC might be a false code as there is no listing of P0457 in the service manual. Mentioned an available ECM reflash related to this DTC that can be done at a Subaru dealer.
3. Initial steps to take: inspect and test the gas cap, power and ground the canister shut-off valve near the canister, and smoke test the system for leaks after removing the hose from the purge solenoid at the engine. Suggested also adding a vacuum gauge to the purge solenoid to monitor for internal leaks.
4. It’s important to put the system in test mode and then smoke test it. Look out for issues with the Vacuum Vent Valves not sealing or not working. The wire harness that feeds the solenoid can break approximately 12 inches up from the connector.

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Final Fix:

• The actual issue was identified as the Evap Tank Pressure Sensor, a part exclusive to Subaru and quite pricey.
• To replace it, the tank had to be taken down.
• Notably, the Evap system showed no leaks.
• The malfunctioning sensor took a while to fail completely. Initially, the code would activate 200 miles after refueling, but over time it began activating just 10 miles post refueling.

Case #2: Dodge

2005 Dodge Neon SXT 2.0L

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Issue + Repair History:

• MIL activated with codes PO456 and PO457.
• After an initial smoke test which found no leaks, the purge solenoid and gas cap were replaced.
• Customer returned with only code PO457. Replaced the gas cap with one from the dealer.
• Customer returned again with code PO457. Gas cap was checked and found to be tightened correctly.
• Prior repair: Purge solenoid replaced due to code PO456.

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Other OBD2 Codes + Test Results:

• Code: PO457 – Gas cap loose
• Test results: Smoke test revealed no leaks.

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Suggestions from the Community:

1. The vehicle uses a sensitive leak detection system (NVLD) capable of detecting very small leaks. For the best results, use the flow gauge on the smoke machine to ensure that when the system is sealed and has reached equilibrium, the flow is zero. If the flow gauge does not indicate zero, start adjusting evap connections until there is movement on the flow gauge.

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Final Fix:

• Used the smoke machine with an increased flow rate of 0.5 l/min. Tracked the lines to the canister and found a hairline crack in it.
• The initial test might not have allowed sufficient time for smoke buildup and the flow rate might have been too low.
• The vehicle, even with less than 30k miles, had a defective evap canister.

Case #3: Ford

2001 Ford Focus SE 2.0L

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Issue + Repair History:

• MIL activated with code P0457 which indicates a problem when PCM detects a fuel tank pressure that is either too high after refueling or has an excessive purge flow rate.
• During testing, the EVAP purge varied between 31% to 60% at idle. The fuel tank pressure sensor consistently read -2.9 in-H2O regardless of the gas cap being on or off.
• The gas cap was replaced.
• Power and ground were applied to the vent solenoid and the EVAP system was pressurized with nitrogen. The pressure showed a slow drop when powered but a quick drop when power was removed from the vent solenoid.
• A Technical Service Bulletin (TSB) suggests using a smoke machine, but the technician did not have access to one.

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Other OBD2 Codes + Test Results:

• Code: P0457 – Fuel tank pressure decrease of more than 7 in. H2O within 30 seconds.

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Suggestions from the Community:

1. Check the vacuum line to the VMV (Vapor Management Valve). If there is regular engine vacuum present, consider replacing the VMV.
2. Build or use a smoke machine to better locate potential leaks in the EVAP system.
3. Verify if the vehicle owner is overfilling (topping off) the fuel tank, which could flood the EVAP system.
4. Inspect the vent line from the charcoal canister for blockages or obstructions.
5. Check the FTP sensor voltage, typically around 2.66-2.7 volts key off engine off.
6. Ensure that the VMV hoses are not melted and that you can blow through the gas cap to verify its functionality.
7. Investigate if any hard plastic vacuum lines leading to the VMV are broken.

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Final Fix:

• The problem was resolved by addressing the VMV (Vapor Management Valve). Ensure there is manifold vacuum going to the VMV on both the large tube to the intake manifold and also on the small vacuum hose. Ground the purge solenoid at idle (350ma) and vacuum should apply to the tank. If the VMV is purging, the fuel trim should change accordingly. The canister purge should have an amp draw of 200ma.

Case #4: Jeep

• 005 Jeep Grand Cherokee Laredo 4.7L

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Issue + Repair History:

• EVAP issues with MIL Lamp on.
• Fault Codes: P0456 (EVAP system-small leak detected), P0457 (EVAP system-loose gas cap), P0440 (EVAP system-General failure), and later P0499 (EVAP system-NVLD solenoid circuit voltage high).
• Previous Repairs:
  • Replaced gas cap (around 6 months prior).
  • Installed a dealer NVLD pigtail connector kit.
  • NVLD solenoid and EVAP canister purge solenoid replaced with dealer parts.
  • NVLD was not switching on/off, so NVLD replaced.
  • NVLD signal wire replaced from PCM C3 connector PIN#35 to NVLD connector.

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Suggestions from the Community:

1. Verify if NVLD is closed by jumpering the connector. The gas cap message will not disappear until a successful forced test or a good trip.
2. Potential harness issue with one bad wire manifesting issues.
3. P0449 is an electrical fault with the vent solenoid circuit. It could be either a failed new NVLD or a harness issue.
4. EVAP issues frequently end up being due to LDP or a checking sensor. After exhaustive testing and checks, consider ECU reprogram/replacement.

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Final Fix:

• The Jeep was fixed by identifying two faulty spades in the NVLD connector. The connector was then replaced with a dealer kit.
  
  *
• NVLD stands for Natural Vacuum Leak Detection and is used primarily by Chrysler and other manufacturers to detect fuel system leaks. Here’s how it works:
• Vacuum Creation: After the vehicle is turned off, the cooling fuel inside the tank creates a vacuum.
• Leak Detection: The NVLD system has a switch that detects this vacuum. If it doesn’t reach a specific level in time, it signals a potential leak, triggering a check engine light.
• Venting: When the vehicle starts, the NVLD system also acts as a vent, releasing excess pressure in the fuel tank.
• It’s a different method from other leak detection systems and is efficient for its purpose.

Case #5: Mazda

1. Vehicle: 2002 Mazda Tribute ES, 3.0L engine.
2. Issue + Repair History: Initially, P0455 (small leak) and P0457 (gas cap loose) codes were found. A leak was discovered at the solenoid valve near the charcoal canister, which was replaced. However, P0455 came back. Smoke tests were done, and codes were cleared multiple times.
3. Other OBD2 Codes + Test Results: P0440 (General EVAP Failure) and P0499 (Vent valve circuit voltage high) were also encountered during the process.
4. Suggestions to Fix Issue: Technicians recommended checking the solenoid under the vehicle below the driver’s seat, replacing the vapor management valve, and checking the NVLD signal wire circuit for shorts or grounds. Replacing the vapor management valve on the left front strut tower and checking the CDV valve were also suggested.
5. Final Fix: The issue was resolved by replacing the vapor management valve located on the left front strut tower.