P0440: Evaporative Emission Control System Malfunction
Key takeaways
- P0440 is a general EVAP fault: the computer saw the fuel-vapor system fail a self-test but didn't pin it to one leak size or one valve.
- It doesn't affect how the engine runs, so it's safe to drive, but the car will fail an OBD emissions inspection until it's fixed.
- Start with the gas cap: tighten it until it clicks, or replace it for $15–$40 if the seal is cracked.
- If the code comes back, a smoke test ($100–$200) finds the leak or bad valve before anyone replaces a $300–$800 charcoal canister.
- Most of the manufacturer bulletins naming P0440 are software updates for the engine computer on Stellantis brands.
What P0440 means
Your car’s fuel-vapor system didn’t pass its own leak or function test. The scanner name is Evaporative Emission Control System Malfunction. The EVAP system catches gasoline vapor from the tank, stores it in a charcoal canister, and later lets the engine burn it through a purge valve. To check it, the engine computer closes the vent valve, seals the system, and watches a tank pressure sensor. P0440 is the general “something is wrong” code in this family: the test failed, but the result didn’t fit a more specific code like P0442 (small leak) or P0455 (large leak).
Is it safe to drive?
Yes. EVAP faults don’t change how the engine runs, and the car won’t lose power. What it costs you is an emissions inspection: most OBD-based smog checks fail a car with the check engine light on. The one thing that changes the answer is a strong raw-gas smell, inside the cabin or around the car after it’s parked. That points to a liquid fuel leak or a badly failed part, not just vapor, and it should be looked at before you keep driving. Our car smells like gas guide covers that case.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Loose, worn or wrong gas cap | Cap doesn’t click, seal is cracked or missing, code set right after a fill-up | $0–$40 |
| Cracked EVAP hose or loose connection | Smoke test shows smoke at a hose or fitting | $100–$300 |
| Vent valve stuck or blocked | Scan tool command doesn’t change tank pressure; valve clogged with dirt or spider webs | $120–$350 |
| Purge valve stuck open | Vacuum at the purge line with engine idling and valve commanded off | $120–$350 |
| Charcoal canister cracked or saturated | Smoke from canister body; charcoal in the lines; history of topping off the tank | $300–$800 |
| Wiring to a valve or tank pressure sensor | Open or short at the connector, often near the tank where road dirt collects | $100–$250 |
| Engine computer software (some makes) | A bulletin for your exact model and year names P0440 | $100–$200, often $0 under warranty |
What to check first
- The gas cap. Tighten it until it clicks. Check the rubber seal for cracks. If it looks worn, a new cap is the cheapest fix there is. Our loose gas cap article explains what to expect after you tighten it.
- Clear it and drive. EVAP is a family where this works. Clear the code once and drive normally for a few days. The system needs specific conditions to rerun its test, often a cold start with the tank between about a quarter and three quarters full. If the light stays off, you’re done.
- Look under the car near the tank. The vent valve and canister usually sit near the tank or the rear axle. Look for a cracked hose, a broken connector, or a valve packed with mud.
- Smoke test. A shop pushes smoke into the sealed system and watches where it comes out. This is the step that stops guessing and usually costs $100–$200.
- Check for bulletins. In the bulletins that name P0440, the pattern is mostly Stellantis brands (Dodge, Chrysler, Jeep, Alfa Romeo, Fiat) releasing engine-computer software updates. On an affected model, ask the dealer about a reflash before you buy parts.
What it costs
The cheap outcome is a gas cap at $15–$40, or nothing at all if tightening it cleared the code. The common outcome is a hose or vent valve at $100–$350 after a smoke test. The expensive outcome is a charcoal canister, around $300–$800. It’s worth paying for diagnosis first: a canister is the part people most often buy on a guess, and a $150 smoke test that points to a $20 hose saves the rest.
Related codes
P0440 often shows up with other EVAP codes: P0441 (purge flow), P0446 (vent control), P0456 (very small leak) and P0455. When several appear together, fix the one that names a specific part first. If the light keeps coming back without a clear pattern, our check engine light comes on and off guide helps, or you can describe what you see to our AI mechanic.
What owners report to NHTSA
31 complaints filed with NHTSA mention P0440, 10 of them since 2015, across 22 different models. The component owners most often filed it under: fuel system, gasoline.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| DODGE DURANGO | 4 | 2003, 2016, 2018 |
| CHEVROLET TRAILBLAZER EXT | 4 | 2003, 2004 |
Manufacturer service bulletins that name P0440
52 technical service bulletins and manufacturer communications filed with NHTSA mention P0440, from 6 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- DODGE CHARGER (2022), bulletin 10243281: Flash: Powertrain Control Module (PCM) Updates Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Tro…
- DODGE CHALLENGER (2022), bulletin 10243280: Flash: Powertrain Control Module (PCM) Updates Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Tro…
- CHRYSLER 300 (2022), bulletin 10243257: Flash: Powertrain Control Module (PCM) Updates Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Tro…
- JEEP WRANGLER (2019, 2020), bulletin 10178668: MIL Lamp On Setting DTC?s P0441, P0456, P0457, P0440
- ALFA ROMEO GIULIA (2017, 2018), bulletin 10170388: Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module (ECM), also known as a Powertrain Control Module (PCM) with the latest available software. Customers may exper…
- JEEP RENEGADE (2018), bulletin 10198416: Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Powertrain Control Module (PCM) with the latest available software. Customers may experience a Malfunction Indicator Lamp (MIL) illu…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can a loose gas cap cause P0440?
Yes. The cap is part of the sealed system the computer tests, and a loose or worn cap is the first thing to rule out. Tighten it until it clicks, then give the code a few days of normal driving to clear.
Is P0440 serious?
Not for the engine. It's an emissions fault, and the car drives normally. The costs are a failed smog or OBD inspection and, if the leak is real, a fuel smell and a little wasted gas.
How much does it cost to fix P0440?
From $15 for a gas cap to about $800 for a charcoal canister at an independent shop. The common middle outcome is a vent valve or a cracked hose at $100–$350. A smoke test for $100–$200 tells you which one you have.
Will P0440 clear itself?
It can. If the cause was a loose cap, the light usually goes off after several drive cycles once the system passes its test again. If it comes back, something is still leaking or a valve isn't working.
What's the difference between P0440 and P0455?
P0455 means the computer found a large leak. P0440 is the general EVAP fault code, used when the test failed without a more specific result. The first checks are the same for both.