P0440 to P0457: evapourative emission leak
The system that keeps fuel vapour inside the tank has found a leak. The code gives its size: P0442 small, P0456 very small, P0455 large, and P0457 a fuel cap that is loose or missing.
SeverityLowLittle risk to the car, but the fault stays until it is repaired.
Can you keep driving?Safe to drive, book a checkWhat does P0442 mean?
Vapour from the fuel tank is stored in a charcoal canister and burnt in the engine instead of escaping into the air. At certain moments the computer seals the system and checks whether it holds pressure or vacuum. If it does not, it reports a leak, sized by how fast the pressure changes. P0440 is the general fault for the system.
What causes P0442?
- A fuel cap that is loose, cross-threaded or has a worn seal
- A cracked vapour hose or a loose connection
- A purge or vent valve that does not close
- A cracked charcoal canister or a leaking filler neck
What to check first for P0442
- Check the cap first: tighten it until it clicks and look at its seal
- Look for cracked hoses around the canister and the filler neck
- A workshop finds small leaks quickly with a smoke test
- After a repair the light goes out by itself only once the system has tested itself again, which can take a few days of driving
Can you drive with P0442?
Safe to drive: it does not change how the car runs, although you may smell fuel. Have it fixed all the same, because vapour escapes into the air and the lit light can hide a second, more serious fault.
Clear a code only after the fault is fixed. A code that comes back means the cause is still there, and a warning light left on can hide a second fault behind the first.
Codes on this page
- P0440Evaporative Emission System
- P0442Evaporative Emission System Leak Detected (small leak)
- P0455Evaporative Emission System Leak Detected (large leak)
- P0456Evaporative Emission System Leak Detected (very small leak)
- P0457Evaporative Emission System Leak Detected (fuel cap loose/off)
Related codes
Checked on · Rafael Soares
These are the generic meanings every manufacturer shares. Each brand adds its own detail, so your car's handbook, its service information and a qualified mechanic have the last word. OdoKeep has no connection with any manufacturer, and the app does not read codes from the car.
