Code Definition

P0440 — Evaporative Emission Control System Malfunction

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0440

P0440 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0440 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The engine control module (ECM) sets this code when it detects a general fault in the evapourative emission control (EVAP) system, which prevents fuel vapours from escaping into the atmosphere. This could be due to a large or small leak, a faulty component, or a failure in the system's pressure or purge flow monitoring. The ECM uses pressure sensors and purge flow data to verify system integrity.

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