P0456 on Chrysler: How to Diagnose & Fix
Evaporative Emission Control System Leak Detected (Very Small Leak)
1 Chrysler model · 2 documented issues · $20-$500 repair
P0456 on Chrysler by model: symptoms, diagnosis and fix
Evaporative emission control system develops small leaks triggering P0456 code. Most commonly failed gas cap, chaffed EVAP purge pipe harness, or failed purge solenoid. Triggers check engine light and prevents emissions testing pass.
Common Symptoms
- Check engine light with P0456 code
- "Gas cap" warning even with cap tight
- Fuel smell near vehicle
- Failed emissions test
- No performance or drivability issues
How to Fix
Start with gas cap replacement ($20-40). If code returns, smoke test EVAP system to locate leak. Common fixes: replace purge solenoid, repair chaffed wiring harness, or replace cracked EVAP hoses.
Sources for this issue (1)
The Chrysler 300 uses Chrysler's proprietary natural-vacuum leak detection hardware instead of a conventional pressure-based leak detection pump. On 2005-2006 cars this is the NVLD (Natural Vacuum Leak Detection) valve/solenoid; from 2007 onward it is the ESIM (Evaporative System Integrity Monitor), a small spring-and-diaphragm switch mounted on or next to the charcoal/vapor canister on the left underbody ahead of the fuel tank. Both work the same way: as the sealed EVAP system heats and cools, natural pressure/vacuum changes trip an internal switch the PCM reads to confirm the system is sealed. The diaphragm seal inside the NVLD/ESIM is a well-documented high-failure item — it stiffens, sticks, or loses its seal with age, so the PCM can no longer verify integrity and falsely reports a leak. The result is a check-engine light with P0456 (small leak, ~0.020 in.), P0455 (large leak), or P0457 (interpreted as loose/missing cap), even when the fuel system is actually sealed. Because the code wording points at the gas cap, this is very commonly misdiagnosed: owners and shops replace the cap (and often the purge valve and canister) repeatedly before discovering the NVLD/ESIM itself is the culprit. One 2012 300 SRT owner reported eight dealer visits — the ESIM and its seal replaced twice, plus a new filler neck, purge valve, and charcoal canister — before the leak code was resolved. The fault is an emissions/MIL issue only: it does not affect drivability or engine longevity, but it will fail an emissions/smog inspection and on some model years can disable remote start until cleared. A faint fuel-vapor smell is occasionally reported when an actual leak is present.
Common Symptoms
- Check engine light / MIL on with no drivability change
- Stored EVAP leak codes P0455, P0456, and/or P0457
- Dashboard or message-center warning that the gas cap is loose/off even when it is tight
- Repeat check-engine light after replacing the gas cap
- Failed state emissions / smog inspection
- Remote start disabled until the code is cleared (some model years)
- Occasional faint fuel-vapor smell near the tank/filler when an actual leak is present
How to Fix
Always start with the cheapest checks: tighten the fuel cap fully (listen for clicks), inspect the cap's O-ring seal, and replace a cracked/old cap with a genuine Mopar cap, then clear the code and drive several drive cycles. If the code returns, have a shop perform an EVAP smoke test — but note the small-leak verification monitor can fail even when a smoke test passes (some hairline EVAP-line cracks only open under vacuum, sealing under the positive pressure of a smoke machine). Inspect the EVAP lines and the purge valve/solenoid for cracks. If the cap, lines, and purge valve are good, replace the NVLD valve (2005-2006) or the ESIM (2007+); the ESIM is the common Mopar service part (e.g., P/N 4861959AD), typically about $40-$60 OEM ($20-$50 aftermarket), and unbolts from the canister with a few hand tools — a DIY-friendly job. On early cars where the NVLD/ESIM is integrated and sold only with the charcoal canister assembly, expect a higher parts cost. After replacement, clear the codes and complete the EVAP drive-cycle/monitor before re-testing for emissions. Total at a shop generally runs from roughly $150 (ESIM swap with labor) up to the $417-$476 range if a full vapor/charcoal canister assembly is needed.
Sources for this issue (1)
P0456 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0456 mean on a Chrysler?
P0456 stands for "Evaporative Emission Control System Leak Detected (Very Small Leak)." This emissions code means the evaporative emission (EVAP) control system has detected a very small leak — even tinier than the one flagged by P0442, roughly equivalent to a 0.020-inch hole. The EVAP system traps fuel vapors from the tank and prevents them from escaping into the atmosphere, and the computer tests for leaks by sealing the system and watching for pressure or vacuum loss. Because the leak is so small, the cause is often subtle, but a loose or worn gas cap is still the most common and easiest to check. It generally indicates a minor seal, hose, or valve leak somewhere in the fuel vapor system. On Chrysler it is documented across 1 model: 300.
What are the most common causes of P0456?
The most common causes of P0456 are: Loose, worn, or faulty gas cap or cap seal, Cracked or loose EVAP hose or line, Leaking vent valve or purge valve not sealing, Damaged O-ring or seal at the fuel filler neck, Small crack or leak in the charcoal canister, Leaking fuel tank or sending unit gasket, Loose or corroded EVAP component connection. The specific cause varies by vehicle.
How much does it cost to fix P0456 on a Chrysler?
Published repair estimates on Chrysler range from $20 to $500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0456 on a different make?
View P0456 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.