Disclosure: This post contains affiliate links. If you make a purchase through these links, I may earn a small commission at no extra cost to you.
A P0440 code (‘Evaporative Emission Control System Malfunction’) on a Jeep, Dodge, Chrysler, or Ram is a broader, more general EVAP code than P0442 (small leak) or P0455 (large leak). Where those two codes point to a specific leak size detected during a test, P0440 typically means the EVAP system isn’t behaving as expected overall — often because a component responsible for running the test itself isn’t working correctly.
On Stellantis/FCA vehicles specifically, this code has a strong association with two components that are somewhat unique to this manufacturer: the Leak Detection Pump (LDP) on older models, and the Natural Vacuum Leak Detection (NVLD) module on newer ones.
What Does P0440 Mean on a Jeep, Dodge, or Chrysler?
The EVAP system captures fuel vapors and routes them to the engine to be burned. To verify the system is sealed properly, the ECM periodically runs a leak test — on FCA vehicles, this is historically done either by a Leak Detection Pump that pressurizes the system and monitors how quickly pressure bleeds off, or by a Natural Vacuum Leak Detection module that monitors natural pressure changes in the fuel tank as it heats and cools.
P0440 sets when the overall EVAP system check doesn’t complete successfully or returns results outside the expected range — which can mean an actual leak, but very often means the test equipment itself (the LDP or NVLD module) has failed or is stuck.
Common Causes
1. Leak Detection Pump (LDP) Failure
Used on many Jeep, Dodge, and Chrysler models through the mid-2000s to mid-2010s, the LDP is a small electric pump mounted near the EVAP canister that pressurizes the system for the leak test. LDP failure is one of the most frequently reported causes of P0440 on these vehicles:
- Internal pump/seal failure — the LDP’s internal diaphragm and seals degrade with age, eventually causing the pump to fail to build or hold the test pressure.
- Stuck switch valve — the LDP includes a switching valve that can stick, preventing the unit from cycling between test and vent modes correctly.
- Wiring/connector corrosion — the LDP is often mounted in an area exposed to road spray, and its connector can corrode over time.
2. NVLD Module Issues (Newer Models)
On newer Jeep, Ram, and Dodge models, the NVLD module monitors natural vacuum/pressure changes in the fuel tank without an active pump:
- Failed internal switch/sensor — the NVLD module’s internal pressure switch can degrade, causing it to report inconsistent results even with no actual leak.
- Module mounted near the fuel tank — exposure to road salt and debris over time can corrode the module’s connector or housing.
3. Gas Cap and Fuel Tank Seal
- Loose, damaged, or wrong gas cap — as with most EVAP codes, a worn or improperly seated gas cap is one of the first things to check, and the cheapest to rule out.
4. Purge Solenoid and EVAP Canister
- Purge solenoid stuck open or closed — can prevent the system from reaching the pressure/vacuum levels needed for the test to complete properly.
- Cracked EVAP canister or hose connections — a genuine leak large enough to prevent the system from holding pressure during the test.
Engine/Model Notes
P0440 isn’t tied to a specific engine family the way thermostat or misfire codes are — it’s an EVAP system code shared across the Pentastar V6, HEMI V8, and Tigershark 4-cylinder lineups. That said, the LDP-equipped era (roughly 2002-2012 on many Jeep Grand Cherokee, Liberty, Dodge Durango, Caravan, and Ram 1500 models) sees P0440 disproportionately tied to LDP failure, while NVLD-equipped vehicles (most models 2013+) see it more often tied to gas caps and the NVLD module itself.
Symptoms of P0440
- Check Engine Light with P0440 stored, sometimes alongside P0455 or P0456
- No drivability symptoms in most cases — the engine runs normally
- Occasionally, a faint fuel odor if there’s a genuine leak large enough to be noticeable
- Code may be intermittent if it’s related to an LDP/NVLD component that only fails the test under certain temperature/fuel-level conditions
How to Diagnose P0440
- Check the gas cap first. Inspect the seal for cracking or damage, and make sure it’s tightened until it clicks. This rules out the cheapest possible cause before moving on.
- Identify whether your vehicle has an LDP or NVLD system. Generally, older models (roughly pre-2013) use an LDP mounted near the canister; newer models use an NVLD module near the fuel tank. This determines which component to focus on.
- Listen for the LDP cycling. On LDP-equipped vehicles, you can sometimes hear the pump cycle briefly with the key on, engine off. No sound, or a sound that doesn’t stop, can indicate a stuck switch valve or failed pump.
- Check for additional EVAP codes. P0440 alongside P0442 or P0455 suggests an actual leak; P0440 alone, especially if intermittent, more often points to the LDP/NVLD component itself.
- Smoke-test the EVAP system if a leak is suspected. A smoke machine connected via the appropriate service port will reveal leaks at hose connections, the canister, and seals.
How to Fix P0440
| Cause | Fix | Typical Cost |
|---|---|---|
| Worn/loose gas cap | Replace gas cap (OEM-spec) | $15-$40 |
| Leak Detection Pump (LDP) failure | Replace LDP assembly | $120-$300 |
| NVLD module failure | Replace NVLD module | $100-$250 |
| Purge solenoid stuck | Replace purge solenoid | $50-$150 |
| Cracked canister/hose leak | Replace affected component | $100-$350 |
Diagnosing P0440 with an OBD2 Scanner
Confirming whether the LDP or NVLD module is cycling correctly often requires watching live data or running a manufacturer-specific EVAP system test. The BlueDriver Bluetooth Pro reads enhanced data on many FCA/Stellantis models and shows EVAP monitor status, which helps confirm whether a fix has actually resolved the underlying test failure.
The Autel AL619 is a solid budget option for reading and clearing the code and checking basic monitor status afterward.
For actively testing the purge solenoid and (on supported models) running an EVAP system test, the THINKCAR ThinkDiag 2 supports bidirectional EVAP component tests on many FCA/Stellantis vehicles, which can help isolate whether the LDP/NVLD or a valve is the actual problem before replacing parts.
Frequently Asked Questions
What’s the difference between P0440, P0442, and P0455?
P0442 and P0455 point to specific leak sizes detected during the EVAP test (small and large, respectively). P0440 is more general — it indicates the overall EVAP system check didn’t complete or pass as expected, which can be caused by an actual leak, but is also commonly caused by a failed Leak Detection Pump or NVLD module that runs the test itself.
How do I know if my vehicle has an LDP or an NVLD module?
Generally, FCA/Stellantis vehicles built through roughly 2012 use a Leak Detection Pump (LDP) mounted near the EVAP canister, while most models from roughly 2013 onward use a Natural Vacuum Leak Detection (NVLD) module mounted near the fuel tank. Checking your specific model year against the factory service manual (or having a shop confirm) is the most reliable way to know which system you have.
Is P0440 dangerous to drive with?
No. Like other EVAP codes, P0440 is emissions-related and doesn’t affect engine performance or safety. It will cause a failed emissions inspection in jurisdictions that check for stored codes.
Can a bad gas cap really cause P0440 (not just P0455)?
Yes. While a missing or very loose gas cap more classically triggers P0455 (large leak), a moderately worn cap seal can sometimes cause the overall EVAP system check to fail in a way that registers as P0440, especially on vehicles where the test relies on the system holding a specific pressure/vacuum range.
How much does it cost to fix P0440 on average?
It depends heavily on the cause. If it’s the gas cap, expect under $40. If it’s an LDP or NVLD module — the most common dedicated-component cause — expect somewhere in the $100-$300 range for the part, plus labor, which is usually moderate since these components are reasonably accessible on most models.
Related Diagnostic Guides
- Jeep/Dodge/Chrysler P0128 Code Guide — another common code across this same vehicle lineup
- Chevy P0442 Code Guide — how a similar small EVAP leak is diagnosed on GM vehicles
- Honda P1456 Code Guide — how Honda’s EVAP leak detection differs (fuel tank side)
- BlueDriver vs Autel AL619 — scanner comparison for EVAP monitor status
