Emission Systems Overview

The engine control module has the task of monitoring and controlling certain emission control functions which include:
- Fuel Tank Evaporative Emission Purge Control
- Fuel tank and evaporative system leak detection
- Secondary Air Injection

Other emission control systems function independently of the ECM but can affect proper engine operation and cause faults to set in the ECM based on failures of the following mechanical emission control systems.
- On-board Refueling Vapor Recovery
- Crankcase Ventilation

Understanding the operating parameters of these functions is required in order to properly diagnose an emission related fault.