P0440: the fuel vapour system has a fault
The evaporative emission system seals petrol vapour inside the fuel tank instead of letting it escape into the air, then, at certain times, purges it into the engine to be burnt rather than wasted. This code means the engine control unit has found something wrong with that system without narrowing it down to a specific leak size or purge fault. It sits alongside the more specific leak and purge codes as the general evaporative system fault.
You might notice
- No symptom you'd feel while driving, beyond the engine warning light coming on
- evaporative emission system
- — seals petrol vapour inside the fuel tank instead of letting it escape into the air
What the code itself says
P0440 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Fuel vapour system — Catching fuel vapour from the tank and burning it off in the engine. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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