Service function guideEVAP System Leak Test

This guide covers the complete process for finding fuel vapour leaks in an EVAP (Evaporative Emission Control) system using a smoke machine and a scan tool, written for working mechanics and serious DIYers who already understand basic engine operation. It explains how the system works, when a leak test is required, how to prepare the vehicle, and then walks through the full step-by-step procedure from initial scan to final verification. You will learn how to interpret smoke patterns, pressure readings, and scan-tool data to pinpoint leaks at the cap, lines, canister, purge valve, or tank, and how to confirm the repair with a monitor reset and drive cycle. By the end, you will be able to perform a professional-grade EVAP leak test safely and efficiently across a wide range of vehicles.