Engine Controls - Theory & Operation: Introduction

NOTE: The CHECK ENGINE light is now referred to as Malfunction Indicator Light (MIL). The MIL is displayed in instrument cluster as CHECK ENGINE. Electronic Control Module (ECM) may also be referred to as Powertrain Control Module (PCM). This is the same component.

This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar.