P0456 on 2007-2009 Chrysler Aspen: EVAP Small Leak Causes and Fixes

What's Unique About the 2007-2009 Chrysler Aspen

On this generation of Chrysler SUV and its platform-mate, the Dodge Durango, the P0456 code is very frequently traced back to a specific component: the Evaporative System Integrity Monitor (ESIM). Unlike a simple hose leak, the ESIM can fail internally without any visible external signs, often causing a persistent code even after a smoke test shows no leaks. Owners often replace the gas cap first, only to find the problem is this relatively inexpensive but critical sensor 🎬 Watch: This quick video shows the most common Aspen fix. located on the charcoal canister.

Symptoms You May Notice

• Check Engine Light is on
• "GAS CAP" message on the instrument cluster display
• A faint fuel smell near the rear of the vehicle (less common)

Most Likely Causes

1. Failed EVAP System Integrity Monitor (ESIM) 🔴 High Probability → Shop Evaporative Emissions System Leak Detection Pump The ESIM contains a delicate, weighted switch that detects pressure changes. This switch is a known failure point on many Chrysler products of this era, including the Aspen and Durango, failing electrically or mechanically without creating an external leak a smoke test would find. The internal mechanism can get stuck, leading the computer to believe there is a leak.
   How to confirm: Locate the ESIM on the EVAP canister (under the vehicle, near the driver's side frame rail, in front of the gas tank). Remove it by disconnecting the electrical plug, hose, and twisting it counter-clockwise about a quarter turn. A functioning ESIM should make a rattling sound from the internal weights when shaken; if it is silent or the internal component is visibly broken, it has failed.
   Typical fix: Replace the ESIM and the corresponding O-ring/seal. This is a simple twist-off, twist-on part. 🎬 Watch: How to remove and replace the ESIM unit. The removal process involves depressing a small plastic tab to allow the unit to rotate.
   Est. part cost: $30-$50
2. Faulty EVAP Canister Purge Valve/Solenoid 🟡 Medium Probability → Shop Vapor Canister The purge valve can become stuck partially open due to carbon buildup or wear, creating a constant small vacuum leak that the system detects. It's a common failure item on many vehicles.
   How to confirm: The purge valve is located on the firewall, tucked away near the brake booster, making it hard to see. Disconnect the valve and attempt to blow through it. When unpowered, it should be closed, and no air should pass through. If you can blow through it, it is stuck open and needs replacement.
   Typical fix: Replace the purge valve. Access is tight due to its location on the firewall. One owner documented the successful replacement on a 2007 Aspen, confirming it resolved the code.
   Est. part cost: $25-$50
3. Loose or Faulty Gas Cap 🟡 Medium Probability → Shop Fuel Tank Cap
   How to confirm: First, ensure the gas cap is tightened until it clicks several times. Inspect the cap's rubber O-ring for cracks, dryness, or damage. If the seal is compromised, the cap cannot hold pressure. A smoke test may also indicate a leak at the cap.
   Typical fix: Tighten or replace the gas cap. It is highly recommended to use an OEM Mopar gas cap, as some aftermarket caps are known to cause sealing issues and may not resolve the code.
   Est. part cost: $15-$30
4. Cracked or Disconnected EVAP Hoses ⚪ Low Probability
   How to confirm: Visually inspect all accessible EVAP hoses running from the fuel tank, to the charcoal canister, and up to the purge valve in the engine bay. Look for brittle, cracked, or disconnected lines, especially at connection points. The most definitive method is to have a mechanic perform a smoke test, which fills the system with visible vapor to pinpoint the exact location of any leak.
   Typical fix: Replace the damaged section of hose and secure it with clamps.
   Est. part cost: $10-$40

Rare But Worth Checking

• Cracked Charcoal Canister: → Shop Vapor Canister While not common, the plastic housing of the charcoal canister can develop hairline cracks over time, creating a small leak. This would typically be found during a smoke test and may be related to TSB 25-003-07 where loose charcoal can damage other components.
• Leaking Fuel Filler Neck: → Shop Fuel Filler Neck Corrosion or damage to the metal tube leading to the gas tank can cause a leak. This is usually accompanied by a fuel smell during refueling and is found with a smoke test. There was a recall on the fuel filler neck for some Aspens which could cause fuel spit-back, and subsequent work in this area could potentially lead to EVAP leaks if not sealed correctly.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0456 is present.
2. Inspect the gas cap. Remove it, check the seal for damage, and retighten it until it clicks multiple times. Clear the code and drive for a few days to see if it returns.
3. If the code returns, locate the EVAP System Integrity Monitor (ESIM) on the charcoal canister under the vehicle, along the driver's side frame rail.
4. Disconnect the electrical plug and hose, then press the release tab and twist the ESIM counter-clockwise to remove it. Shake the ESIM. If it does not rattle, it has likely failed and needs to be replaced.
5. If the ESIM seems okay, locate the purge valve on the engine firewall, near the brake booster. Disconnect it and try to blow through it. If air passes, the valve is stuck open and must be replaced.
6. If the above steps do not reveal the cause, the next step is a professional smoke test to find hairline cracks in hoses, the charcoal canister, or the fuel filler neck.

Parts You'll Likely Need

• EVAP System Integrity Monitor (ESIM) / Leak Detection Switch (OEM #04861959AA (superseded by 04861959AB, 04861959AC, 04861959AD)) — This is the most common failure point for the P0456 code on the Chrysler Aspen. It fails internally, causing a persistent code that a smoke test won't find.
  Trusted brands: Mopar, Dorman (p/n 310-219), Standard Motor Products (SMP)
  OEM price range: $30-$45
  Aftermarket price range: $25-$40
• ESIM Seal / Gasket (OEM #52129436AA) — This seal should be replaced anytime the ESIM is removed to ensure a proper seal on the charcoal canister. Some new ESIMs do not include it.
  Trusted brands: Mopar
  OEM price range: $5-$10
  Aftermarket price range: $3-$8
• Vapor Canister Purge Valve / Solenoid (OEM #04891739AB (supersedes 4891739AA)) — This valve can stick open, causing a small, continuous leak. It's a frequent cause after the gas cap and ESIM have been ruled out.
  Trusted brands: Mopar, Bosch, Dorman (p/n 911-202)
  OEM price range: $35-$60
  Aftermarket price range: $20-$40
• Fuel Cap (OEM #52124512AA) — A worn-out seal on the gas cap is a simple and common cause for all EVAP codes. Always check this first. Using an OEM cap is strongly recommended.
  Trusted brands: Mopar, Stant
  OEM price range: $20-$30
  Aftermarket price range: $10-$20

Related Codes That Often Appear With This One

• 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 or if the ESIM failure mimics a gas cap leak.
• P0455 — This code indicates a large EVAP leak. A component like the ESIM or purge valve can fail intermittently, sometimes triggering a small leak code (P0456) and other times a large leak code (P0455).

Technical Service Bulletins (TSBs) & Recalls

• 25-003-07 - DTC P0456 - Evaporative System Small Leak Due To Loose Charcoal From Canister
• 18-009-09 - Flash: Drivability Improvements (Addresses erroneous EVAP codes)
• Bulletin #1809223 - Notes that P0456 may be set alongside P0440, P0441, or P0455 and involves reprogramming the PCM.
• Bulletin #1804823 - References the use of the wiTECH Small Leak Verification Test (SLVT) specifically for diagnosing P0456.
• Bulletin #18-089-24 - Suggests using the wiTECH Small Leak Verification test (SLVT) to determine if a leak is present when P0456 is found with catalyst efficiency codes.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB 25-003-07) was issued for the 2007 Aspen for code P0456. It notes that loose charcoal from a deteriorating canister can contaminate the EVAP system, potentially causing the ESIM or other valves to malfunction. If charcoal particles are found when removing the ESIM, the entire charcoal canister may need replacement.
• Another TSB (18-009-09) involves a PCM software update that can address erroneously set EVAP codes, including P0456, by adjusting the sensitivity of the leak detection monitor.

Mechanic-Grade Diagnostic Values

• ESIM Switch Voltage (Scan Tool Data) — expected: Approximately 4.5 volts when the switch is open (system not pressurized).. Failure: Voltage does not change from 4.5V when vacuum is applied, or reads 0V, indicating a circuit or switch issue. The switch should close (voltage drops) at approximately 1 inch of water column pressure.
• Purge Solenoid State Test — expected: No air should pass through the valve when it is unpowered (electrically disconnected).. Failure: If you can blow air through the valve when it is disconnected, it is stuck partially open and is faulty.

Scan Tool Commands That Help

• Chrysler WiTech or equivalent professional scan tool: EVAP Monitor Test / ESIM Forced Monitor Test — This function forces the PCM to run the EVAP leak test on demand, rather than waiting for specific drive cycle conditions. It is used to verify a fix without having to drive the vehicle for several days. A technician can run the test, see if it passes or fails, and check for pending codes immediately.
• Chrysler WiTech or equivalent professional scan tool: Purge Solenoid Actuation — This bidirectional control allows a technician to command the purge solenoid open (typically in 10% increments) while the engine is running. It is used to verify the solenoid's electrical circuit and mechanical operation. When activated, a change in engine RPM or fuel trims should be observed.

Wiring & Ground Locations

• G113 / G114 — Located at the left front of the engine compartment.. These are primary grounds for the engine control system. A poor connection here could cause erratic sensor readings and phantom codes, although it's not a primary suspect for a lone P0456.
• G208 — Located in the left kick panel area, inside the cabin.. This ground serves various interior and data line components. While not directly tied to the EVAP system, verifying major grounds is good practice when electrical issues are suspected.
• ESIM Connector — On the ESIM itself, mounted to the charcoal canister under the driver's side of the vehicle.. This 2-pin connector provides power and ground for the ESIM's internal switch. Corrosion or damage to these pins or wires can cause the PCM to lose its signal from the switch, mimicking a component failure.

Real Owner Repair Stories

• YouTube user Cams C. (2007 Chrysler Aspen) — Check Engine Light with code P0456 (very small EVAP leak).
  ❌ Tried (didn't work) The owner noted that in past experiences, tracing lines for a leak was time-consuming and often fruitless.
  ✅ What actually fixed it The owner went straight to replacing the EVAP canister purge valve, which was hidden on the firewall near the brake booster. After replacement and a 25+ mile drive cycle, the check engine light did not return, confirming the fix.
• ChryslerForum.com user (2007 Chrysler Aspen) — "gascap" message on the dash, plus codes P0456 and P0457.
  ❌ Tried (didn't work) Replacing the gas cap (twice)., Having a smoke test performed, which found no leaks.
  ✅ What actually fixed it The owner replaced the entire vapor canister assembly because the ESIM was not sold separately at the time. This resolved both the codes and the dash message. Another user in the same thread later confirmed that replacing just the ESIM (which became available separately) also solved their identical issue.
• NHTSA ODI #11281463 — An owner reported a gasoline odor and a check engine light with code P0456 upon starting the vehicle.
• NHTSA ODI #11076128 — A driver experienced a P0456 code for a small leak and reported that the vehicle would shut down, despite no visible leaks being found.

"I Checked Everything" — The Actual Cause

• A very common scenario for the Chrysler Aspen is for a professional smoke test to show no visible leaks, yet the P0456 code persists. The root cause is an internal mechanical or electrical failure of the Evaporative System Integrity Monitor (ESIM). The ESIM's job is to detect pressure changes via a weighted switch; this switch can get stuck or fail electronically without creating an external leak path for smoke to escape. Technicians and owners often confirm this by replacing the ESIM, which resolves the code.

OEM Part Supersession History

• 04861959AA → 04861959AB, 04861959AC, and finally 04861959AD. — Standard part revisions to improve reliability and address failure modes.
  Heads up: The latest part number, 04861959AD, is specified as the correct service replacement for the original and is widely compatible with many Chrysler/Dodge/Jeep vehicles from this era and beyond. There are no known incompatibilities when using the newest revision on an older vehicle like the Aspen.

Model Year Variations Within This Range

• 2008-2009: For 2008, an upgraded 4.7L V8 was introduced. For 2009, the 5.7L Hemi V8 received a power increase and a Hybrid model was offered. However, the fundamental design of the ESIM-based EVAP system that is central to the P0456 code remained consistent across all engine options for the 2007-2009 model years.

Diagnostic Flowchart

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0457 — Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off). Often appears alongside P0456 on the Aspen, as noted by owners experiencing the 'GAS CAP' message on the dash.
• P0442 — Evaporative Emission Control System Leak Detected (Small Leak). Shares the exact same root causes as P0456, including a faulty ESIM, stuck purge valve, or loose gas cap.
• P0455 — Evaporative Emission Control System Leak Detected (Gross Leak). Can be triggered by a completely failed gas cap seal or severely cracked EVAP hoses that would otherwise cause a P0456 if the leak were smaller.
• P0441 — Evaporative Emission Control System Incorrect Purge Flow. Directly related to the EVAP Canister Purge Valve/Solenoid, which is a common failure point on the Aspen that also causes P0456.

Frequently Asked Questions