This Just in Time Training program contains four animated sections describing how the vehicle PCM processes sensor data to calculate injector on-time. Finally: a program that explains this important process. It also includes an extensive explanation of how fuel trim maintains the correct air/fuel ratio, and then alerts the onboard diagnostic system to excessive fuel corrections.

Chapter 1 - Fuel Trim 1

Chapter 2 - Fuel Trim 2

Chapter 3 - Volumetric Efficency