P0456 on 2012-2019 Chrysler 300: EVAP Small Leak Causes and Fixes

What's Unique About the 2012-2019 Chrysler 300

The 2012-2019 Chrysler 300 belongs to the second generation (LD). A key difference within this range is that models from 2015 onward may feature a capless fuel filler system, which can sometimes be the source of the leak if the spring-loaded flap fails to seal or gets dirty. Chrysler vehicles of this era also use a specific type of leak detection system, an Evaporative System Integrity Monitor (ESIM), which replaced the older Leak Detection Pump (LDP). This ESIM uses natural vacuum changes in the tank as the car cools down to test for leaks. A common failure is the ESIM module itself, which can get stuck or have a bad seal, falsely triggering a P0456 code even when no other leak exists.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• "Gas Cap" or "Loose Fuel Cap" message on the dashboard (even on capless models)
• Remote start may be disabled
• A faint smell of fuel, particularly after refueling (this is rare for a small leak but can occur if the leak is near the cabin or under the hood)

Most Likely Causes

1. Loose, worn, or incorrect gas cap 🔴 High Probability → Shop Fuel Tank Cap The gas cap is the most frequently handled part of the EVAP system. Aftermarket caps are notorious for not sealing correctly and causing a P0456 code. The seal can also dry out and crack over time.
   How to confirm: Ensure the cap is tight (clicks at least three times). Inspect the cap's rubber seal for cracks, stiffness, or brittleness. For 2015+ capless systems, inspect the filler neck flap for debris and ensure it moves freely. Clean the sealing surface of the filler neck.
   Typical fix: Tighten or replace the gas cap. It is strongly recommended to use a genuine OEM (Mopar) cap for best results, as aftermarket versions are a common cause of the problem.
   Est. part cost: $20-$50
2. Faulty EVAP Purge Valve/Solenoid 🟡 Medium Probability → Shop Vapor Canister This valve is a very common failure point on Chrysler/Dodge products. It gets stuck slightly open due to carbon buildup or wear, creating a small, constant leak path that the system detects.
   How to confirm: The valve is located on the passenger side of the engine, near the firewall. A simple test is to remove the valve (it unplugs and has two hoses) and try to blow through it. When unpowered, it should be completely closed; if you can blow any air through it, it's faulty and needs replacement.
   Typical fix: Replace the purge valve. This is a straightforward repair that typically takes less than 15 minutes. The part number has been updated over the years; 04891738AC is a common replacement for the original 04891738AA.
   Est. part cost: $30-$80
3. Cracked or disconnected EVAP hose 🟡 Medium Probability The plastic and rubber EVAP lines become brittle from engine heat and age. A common failure point is a hard plastic line that runs near the rear passenger-side wheel well, which can develop hairline cracks. Another potential spot is the hose connected to the purge valve in the engine bay.
   How to confirm: Visually inspect all accessible EVAP hoses for obvious cracks, especially at connection points and bends. A professional smoke test is the most effective way to find a small hose leak, as the crack may be invisible to the naked eye.
   Typical fix: Replace the damaged section of hose. In a documented case, an owner successfully repaired a cracked hard line by cutting out the broken section and splicing in a piece of fuel-rated rubber hose with clamps.
   Est. part cost: $10-$60
4. Faulty Evaporative System Integrity Monitor (ESIM) ⚪ Low Probability → Shop Vapor Canister Chrysler's ESIM leak detection system can fail internally or its O-ring seal can degrade, causing the system to report a leak when none exists. This is a known issue across many Chrysler/Dodge/Jeep vehicles from this era.
   How to confirm: This is typically diagnosed after a smoke test confirms there are no other leaks in the system. If the system holds pressure during a smoke test, the ESIM itself is the prime suspect. The ESIM is a white, plastic component attached to the charcoal canister, located behind the passenger side rear wheel well liner. 🎬 Watch: Locating and replacing the ESIM and charcoal canister
   Typical fix: Replace the ESIM and its associated O-ring seal. The part twists into the canister and is secured by a small tab.
   Est. part cost: $25-$70

Rare But Worth Checking

• Cracked EVAP Canister: → Shop Vapor Canister The charcoal canister itself can develop hairline cracks from road debris impact or age. It is located in the rear passenger side wheel well area. A smoke test is the best way to confirm a leak here, as it may not be visible.
• Leaking Fuel Tank Filler Neck: → Shop Fuel Tank Corrosion or physical damage to the metal tube leading to the gas tank can cause a small leak. This is less common but can happen, especially in regions with heavy road salt use.
• Fuel Pump Module Seal Leak: → Shop Fuel Pump The O-ring seal for the fuel pump module, located under the rear seat, can degrade and cause a leak. This is often accompanied by a distinct fuel smell inside the car. A technician in one video lifted the rear seat to check for fuel smell and smoke in this area as part of the diagnosis.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0456 is present. Note any other EVAP codes like P0440, P0441, P0455, or P0457.
2. Inspect the gas cap. Tighten it until it clicks at least three times. If it looks old, the seal is cracked, or it's an aftermarket brand, replace it with a genuine Mopar OEM part. For capless systems (2015+), clean the filler neck opening and ensure the internal flap seals tightly.
3. Clear the code using a scanner or by disconnecting the negative battery terminal for 15 minutes. Drive the vehicle for several days. The EVAP monitor runs under specific conditions (often with the fuel tank between 1/4 and 3/4 full), so the light may not return immediately.
4. If the code returns, perform a basic check of the EVAP purge valve. It's on the passenger side of the engine. Disconnect it and try to blow air through it. If air passes through, the valve is stuck open and must be replaced.
5. Visually inspect the EVAP hoses in the engine bay, especially around the purge valve, for cracks or loose connections.
6. Visually inspect the EVAP canister, ESIM, and hoses in the rear passenger wheel well area for any obvious cracks or damage. You may need to remove the wheel and fender liner for a clear view.
7. If no visual faults are found, the most effective next step is a professional smoke test. This involves feeding low-pressure smoke into the EVAP system's service port to reveal the exact location of the leak.
🎬 See how a professional smoke test finds hidden leaks
8. Based on the smoke test, replace the leaking component. If the smoke test reveals no leaks, the ESIM itself is the most likely cause.

Parts You'll Likely Need

• Gas Cap (OEM #5278632AG) — This is the most common cause due to frequent use and wear on the seal. Aftermarket caps are a frequent source of failure.
  Trusted brands: Mopar (OEM recommended)
  OEM price range: $25-$50
  Aftermarket price range: $15-$30
• Vapor Canister Purge Valve / Solenoid (OEM #04891738AC (supersedes 04891738AA)) — A very common failure point on Chrysler vehicles. It gets stuck partially open, creating a small leak that the system detects.
  Trusted brands: Mopar, Bosch, Dorman
  OEM price range: $30-$80
  Aftermarket price range: $20-$50
• Evaporative System Integrity Monitor (ESIM) (OEM #04861959AD) — This module is the core of the leak detection system and is a known failure point. It can fail internally, causing a false P0456 code even with no physical leak.
  Trusted brands: Mopar (OEM recommended)
  OEM price range: $25-$70
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• P0441 — This code for 'Incorrect Purge Flow' often appears with P0456 when the purge valve is failing, as a stuck valve can cause both a leak (P0456) and improper flow (P0441).
• P0440 — A general 'EVAP System Malfunction' code that can accompany a specific leak code like P0456, indicating a broader issue detected by the PCM.
• P0455 — This code for a 'Large Leak' can sometimes be triggered by the same components (like a failed ESIM or a very bad hose crack) that cause a small leak code, depending on how the component fails or how the test runs.
• P0457 — This code specifically means 'EVAP System Leak Detected (Fuel Cap Loose/Off)'. It often appears alongside P0456 if the system suspects the gas cap is the primary issue.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #18-089-24: Mentions P0456 and advises using the wiTECH Small Leak Verification test (SLVT).
• Bulletin #18-070-20: Lists P0456 as a potential DTC that can be addressed by a PCM software update.
• Bulletin #18-073-20: Lists P0456 as a potential DTC.
• Bulletin #1804823: Specifically references the wiTECH SLVT for diagnosing P0456.
• Bulletin #18-038-20: Recommends using the wiTECH SLVT if P0456 is present.
• Bulletin #18-006-16 REV. A: Notes that a PCM software update can address an illuminated MIL with a P0456 code, among others.

Platform-Specific Known Issues

• Chrysler has issued multiple Technical Service Bulletins (TSBs) that mention P0456, including 18-089-24, 18-070-20, and 18-038-20. These bulletins often don't point to a single faulty part but instead instruct technicians to use the dealer-specific wiTECH Small Leak Verification Test (SLVT) to properly diagnose the source of the leak. This highlights that finding the leak can be complex and that a systematic approach is required.
• A cracked EVAP hose in the passenger rear wheel well area is a documented failure. In a repair video, an owner found a hole in the hard plastic line where it bends. Instead of replacing the entire complex harness, he successfully repaired it by cutting out the damaged section and splicing in a piece of rubber fuel hose with clamps.

Mechanic-Grade Diagnostic Values

• ESIM Natural Vacuum Switch Threshold — expected: The internal switch should close when a natural vacuum of 0.8 to 2.2 inches of H2O develops in the fuel tank as it cools.. Failure: If the system cannot achieve or hold this level of vacuum over multiple cool-down cycles, the PCM logs a P0456 fault. This can be due to a physical leak or a faulty ESIM switch.
• ESIM Bench Test (Off-Vehicle) — expected: With a power probe, apply ground to one pin and connect the test light to the other. The light should be off. When you apply vacuum to the appropriate port, the internal switch should close, and the test light should illuminate (showing ground pass-through).. Failure: If the switch does not close under vacuum or is stuck closed (light on with no vacuum), the ESIM is faulty.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID for ESIM: Advanced scan tools can access OBD2 Mode $06 data, which shows the raw results of the EVAP monitor. A technician can look at the test values and thresholds for the 'ESIM closed state' to see if the monitor is passing, failing, or borderline before a code is set. (see via Professional scan tool with Mode $06 capability.)

Scan Tool Commands That Help

• wiTECH (Chrysler Dealer Tool): Small Leak Verification Test (SLVT) — This is a mandatory test for diagnosing P0456 on 2013+ models. It uses the purge solenoid and fuel tank pressure sensor to force a system test, providing a pass/fail result in minutes instead of waiting days for the natural monitor to run. It must be run before repairs to verify the leak and after repairs to confirm the fix.

Wiring & Ground Locations

• EVAP System Fuses (2014+) — In the under-hood fuse box (left side of engine bay), check fuses F31, F34, F35, and F37.. These fuses are part of the general engine management system that powers the EVAP components. A loss of power can cause system malfunction.
• EVAP System Relays (2014+) — Check relay R63 in the under-hood fuse box and relay R29 in the rear fuse box (in the trunk, behind the battery).. These relays control power to circuits related to the engine and EVAP system.
• G109 (example from similar LX platform) — On the right shock tower in the engine bay, near the purge solenoid.. A poor ground connection for the purge solenoid or other nearby sensors can cause erratic behavior and false codes.

Real Owner Repair Stories

• YouTube channel 'Fix It All' (2015 Chrysler 300 3.6L with 166,000 miles) — Check Engine Light with codes P0456 and P0440.
  ❌ Tried (didn't work) Replaced the EVAP purge valve. The code returned after 7 hours.
  ✅ What actually fixed it The Evaporative System Integrity Monitor (ESIM), also called a leak detection pump, was faulty. The old unit made a rattling sound when shaken, while the new one did not. Replacing the ESIM cleared the codes.

"I Checked Everything" — The Actual Cause

• A professional technician reported a case on a 2013+ Chrysler where the vehicle passed a standard pressure smoke test, but repeatedly failed the dealer's Small Leak Verification Test (SLVT). The cause was a hairline crack in a plastic EVAP line that only opened and leaked under vacuum, which is how the ESIM system naturally tests itself. The positive pressure from the smoke machine was actually sealing the crack, making the leak impossible to find with that method. The fix was to isolate sections of the EVAP line and test them with a handheld vacuum pump until the leaking section was found.
• If a smoke test passes and all hoses appear intact, the most likely culprit is an internal failure of the Evaporative System Integrity Monitor (ESIM). The ESIM contains a switch and weighted valves that can fail or stick, causing the computer to believe there is a leak when the system is actually sealed.

OEM Part Supersession History

• 4861959AA, 4861959AB, 4861959AC → 04861959AD — Standard part revision and improvement by the manufacturer.
  Heads up: The latest part number, 04861959AD, is the correct service replacement for the previous versions.

Model Year Variations Within This Range

• 2013-2019: Models from 2013 and newer are equipped with a Fuel Tank Pressure (FTP) sensor. This sensor is used by the PCM specifically for the wiTECH Small Leak Verification Test (SLVT) and for monitoring purge flow. The primary small leak detection still relies on the ESIM switch state during a natural vacuum cycle.
• 2012: The 2012 model year and older do not have a Fuel Tank Pressure (FTP) sensor. Diagnosis cannot use the SLVT and relies more heavily on traditional smoke testing and checking the ESIM switch function.