What are the common causes of P0440?

Fuel cap loose or sealing poorly. Small leak in EVAP lines or canister. Faulty purge or vent valve. Leaking fuel tank or filler neck seal. Cracked charcoal canister.

Tighten or replace the fuel cap and clear the code first. Smoke-test the EVAP system at tank, canister, and vent. Command the purge and vent valves with a scan tool. Inspect EVAP lines and the canister for cracks. Repair the identified leak and run a full EVAP monitor cycle.

P0440

Evaporative Emission System

System: Auxiliary emission controls (P code)
Lamp: Check Engine Light
Category: Powertrain - Auxiliary Emissions Controls

What it means

P0440 means Evaporative Emission System.

Check these first

Fuel cap loose or sealing poorly
Small leak in EVAP lines or canister
Faulty purge or vent valve
Leaking fuel tank or filler neck seal
Cracked charcoal canister

What to do next

Tighten or replace the fuel cap and clear the code first
Smoke-test the EVAP system at tank, canister, and vent
Command the purge and vent valves with a scan tool
Inspect EVAP lines and the canister for cracks
Repair the identified leak and run a full EVAP monitor cycle

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Updated

Generic SAE J2012 definition. Last updated 2026-08-30.