P0440: Evaporative emission (EVAP) system malfunction
The system that collects petrol vapour from the tank has a fault. The most common cause is a loose fuel cap or a leak in the vapour hoses.
| Code | P0440 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0440 means
The EVAP system stores petrol vapour from the tank in an activated charcoal filter (the canister) and later feeds it to the engine to be burnt. The ECU tests it by sealing it and checking the pressure, and has found a problem without narrowing it down.
Most common causes
- Fuel cap loose or with a worn seal
- Cracked or loose vapour hose
- Faulty canister purge valve
- Faulty canister vent valve
- Damaged or saturated canister
- Faulty fuel tank pressure sensor
Symptoms
- Engine warning light on
- Smell of petrol around the car
- Usually no change in how it drives
Can you drive with P0440?
Yes, no rush It does not affect how the engine runs. You can drive normally and have it checked when convenient, though a smell of petrol should not be left for long.
Open the bonnetthe in-depth explanation
How to check it
First, remove and refit the fuel cap until it clicks and check its seal. Clear the code and see whether it returns after a few days of normal driving.
How to read and clear P0440 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0440 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P043C The catalytic converter temperature sensor (bank 2
- P043D The catalytic converter temperature sensor (bank 2
- P043E The reference opening for detecting fuel vapour leaks has low flow
- P043F The fuel vapour leak detector reference opening has excessive flow
- P0441 EVAP system incorrect purge flow
- P0442 EVAP system small leak detected
- P0443 EVAP purge control valve circuit malfunction
- P0444 EVAP purge control valve circuit open
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0402 Exhaust gas recirculation (EGR) flow excessive
- P0403 EGR control circuit malfunction
What does code P0440 mean?
The EVAP system stores petrol vapour from the tank in an activated charcoal filter (the canister) and later feeds it to the engine to be burnt. The ECU tests it by sealing it and checking the pressure, and has found a problem without narrowing it down.
Can you drive with P0440?
It does not affect how the engine runs. You can drive normally and have it checked when convenient, though a smell of petrol should not be left for long.
How do you clear P0440?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0440 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
