What P0440 means
Evaporative Emission Control System Malfunction
How to diagnose
- Read freeze frame data. When P0440 set, your ECU snapshotted every sensor at that moment. This tells you what the car was doing when the fault triggered — RPM, load, coolant temp, throttle position, fuel trims. Almost always enough info to figure out the cause without further testing.
- Check for related codes. If you have P0440 plus other codes, fix the earliest one in the chain first — a single root cause often triggers multiple codes.
- Cheap fixes first. For most codes, the order is: inspect connectors + wiring (free), check for vacuum leaks (cheap), replace sensor (moderate), replace mechanical part (expensive). Follow that ladder before dropping money on parts.
Manufacturer-specific descriptions
Different manufacturers use P0440 for slightly different failure modes:
| AUDI | Missing fuel cap, Defective or damaged fuel cap, Distorted or damaged Fuel Tank Filler Neck, Torn or punctured Evaporative system hose(s), Defective Fuel Tank Sending Unit gasket or seal, Split or damaged Carbon Canister, Defective Evaporative Vent Valve and or Evaporative Purge Valve, Defective or damaged fuel tank |
| BMW | Evaporative Emission System |
| FORD | Evaporative Emission Control System Malfunction |
| MITSUBISHI | Evaporative Emission Control System Malfunction; EVAP.emission control system |
| NISSAN | Evaporative Emission Control System Malfunction |
| VOLKSWAGEN | Evaporative Emission (EVAP) System |
Read P0440 on your own car
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