Fix P0456: Mechanic’s solutions that WORKED

The code Code P0456: Evaporative Emissions System – Small leak detected signifies a minor leak in the vehicle’s evaporative emission control system, which is responsible for preventing fuel vapors from escaping into the atmosphere. Most often, it is due to a loose gas cap or minor damage in the evaporative system components

P0456 quick overview

Meaning	P0456: Evaporative Emissions System – Small leak detected
Is it serious?	It won’t typically cause immediate driving issues, but it’s important to address it.
Possible causes	– Loose or faulty gas cap – Cracked or rotted hoses in the evaporative system – Faulty purge valve – Damaged or faulty charcoal canister – Issues with the “J” shaped hose on the evap canister – Malfunctioning or deteriorated evap-canister purge solenoid – Faulty filler tube
How to diagnose?	Check the gas cap. Ensure it’s tightened properly (usually until it clicks three times) and inspect for damages. Perform a visual inspection. Look for obvious signs of wear, tear, or damage in the evaporative system hoses, especially the “J” shaped hose on the evap canister. Use a smoke machine. Introduce smoke into the system and look for areas where it may be leaking out. Check the purge valve. Ensure it operates correctly, and there are no signs of malfunction. Evaluate the evap-canister purge solenoid. Confirm that it closes completely after the vehicle starts. Scan for other OBD2 codes. There might be related codes that can provide additional information. Consult a technician or mechanic. If the issue isn’t clear, it’s always a good idea to get a professional opinion.
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 P0456 – learn from mechanics

I looked into P0456 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: BMW

Vehicle Information

• 2001 BMW 325Ci 2.5L

Issue + Repair History

• MIL (Malfunction Indicator Light) is on.
• Code P0456 shown as an undocumented code on scanner.
• Light activated the day after a left front turn signal bulb was replaced by a student.
• Code was cleared but returned immediately on the first drive.

What are People Suggesting to Fix the Issue

• It’s a code for evap leak detected.
• Check all vacuum lines.
• Examine the gas cap as it’s a common issue.
• The code is specifically for an “Evaporative Emission System Leak Detected (very small leak)”.
• Check the charcoal canister with smoke for potential small leaks.
• Examine all EVAP lines and connectors for looseness.
• Look closely near areas where the student worked.
• Use a smoke machine to detect leaks.
• See if a hose was knocked loose when changing the bulb.
• Ensure the mass air flow is plugged in, as it might have been unplugged during bulb replacement.
• There’s a possibility of initializing it with a specific process (turning key on, engine off, waiting, and pressing full throttle).
• Check the code monitors on a scanner.
• Consider whether the light bulb used has the correct wattage.

Final Fix

• Not reported, but I had to include it because of great diagnostic advice.

Case #2: Chrysler

• 2017 Chrysler Pacifica LX 3.6L

Issue + Repair History

• MIL (Malfunction Indicator Light) is on.
• Code PO456 set for a small evap leak.
• ESIM and its seal were replaced but the problem recurred.
• Vehicle came back with the same code multiple times.
• ESIM replaced twice.

What are People Suggesting to Fix the Issue

• Check if the ball stays at zero after shutting off the air and waiting for 10 minutes.
• Inspect for leaking gas caps as they are common on Chryslers.
• Verify if the ESIM might be installed upside down.
• Keep the vehicle overnight and check if the ESIM switch is closed in the morning. Look for natural vacuum due to ambient temperature drop.
• Check for good trips in the event data for any intermittent issues.
• Consider an intermittent leaking purge valve as the potential cause if ESIM isn’t the solution.

Final Fix

• No leaks were found, but after letting the vehicle sit overnight, the ESIM switch was closed.
• Following suggestions from the community and online Chrysler forums, the purge valve was replaced as a potential solution.
  
  *ESIM stands for Evaporative System Integrity Monitor. It’s a component used in a vehicle’s evaporative emissions system. The ESIM’s primary function is to monitor the integrity of the fuel system, ensuring that there are no leaks that could allow fuel vapors to escape into the atmosphere.

Case #3: Lexus

Vehicle Information:

• 2004 Lexus LX470, 4.7L

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Issue + Repair History:

• MIL (Malfunction Indicator Light) on.
• Both VSC Trac and VSC Off lights activated.
• OBD2 codes: P0456 (EVAP code) in the ECM and C1201 in the ABS controller.

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Suggestions from Community:

1. The EVAP code might disable the VSC, and addressing the EVAP issue may also resolve the VSC light.
2. The P0456 EVAP code often relates to a small leak in the evap system. Check the gas cap and the filler neck sealing surface for issues.
3. Smoke test the tank, especially since cracks in the plastic fuel pump have been a common cause of the P0456 code on similar vehicles.
4. If the vehicle is under warranty, consider sending it to the dealer for repair.
5. A malfunction in the engine ECM (as indicated by code C1201) will inhibit the operation of traction control and VSC.

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Final Fix:

• The EVAP code was resolved by repairing a damaged rubber line near the canister and verifying its seal.
• Clearing the codes resolved the VSC and MIL lights issue.

Case #4: Jeep

Vehicle Information:

• 2001 Jeep Wrangler Sahara, 4.0L

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Issue + Repair History:

• Intermittent MIL (Malfunction Indicator Light) activation.
• OBD2 code: p0456 – EVAP small leak.
• Visual inspection conducted on the EVAP system, including hoses, gas cap, solenoids, etc. No apparent rust around the gas cap’s sealing perimeter. Purge solenoid functioned when commanded. Applying vacuum to the LPD resulted in no vacuum retention. Attempt to seal the system using an EVAP smoke cart was unsuccessful.

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Suggestions from Community:

1. Consider trying a new cap for small EVAP leaks in Chryslers.
2. Inspect the white plastic part of the gas cap for rust at the diaphragm.
3. Check the seal at the fuel pump module; might require tank removal. Consider replacing the seal and solenoid if problematic.
4. Inspect the LDP and Purge solenoids for black charcoal pellets, signifying a potential canister rupture.
5. The LDP pump failure is common; monitor the LDP switch state when drawing a vacuum.
6. Ensure the system is properly sealed when diagnosing.
7. Apply ground to the LDP control wire for better sealing.
8. Examine rubber hoses and connectors for possible damage or splits.
9. Check for any bulletins about tank replacement.
10. Pinch off the vent hose and use a smoke test, preferably with dye, for leak detection.
11. Replace the gas cap as Jeep caps are known to be less durable.
12. Examine inside the gas cap, replace if rust is found. Also, inspect the fuel pump o-ring clamp for tightness.

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Final Fix:

• The LDP (Leak Detection Pump) was identified as faulty due to its inability to hold a vacuum. After replacing the LDP pump, the issue was resolved.

Case #5: Volvo

Vehicle Information:

• 2003 Volvo S60 2.4T, 2.4L Engine

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Issue + Repair History:

• MIL (Check Engine Light) on with code P0456 – Evap system very small leak detected.
• Previously replaced a cracked gas cap seal with a new one from the Volvo dealer. However, the light returned shortly after.

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What are people suggesting to fix the issue:

• Check the “J” shaped hose on top of the rectangular evap canister for dry rot cracking.
• Check the fuel tank purge valve, the tank for leaks, and the filler tube.
• Consider software updates as there’s an extended warranty for software-related issues for this code.
• Check the evap-canister purge solenoid as it may not close all the way after startup.
• Ensure the gas cap is tightened properly; it should click three times to ensure it’s sealed.
• Inspect rubber hoses on the fan shroud connected to the evap solenoid, as they can crack from heat.
• Hose from the canister shut-off valve to the canister is common to have small splits.
• The hose between the charcoal canister and the canister shut-off valve may have cracks, particularly at the canister end.

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What was the final fix:

• The intermittent sticking purge valve was replaced, which resolved the issue.