What is used in a truck system ECM or ECU to switch output circuit devices?

A) transistors
B) sensors
C) relays
D) transformers

ECM

Stands for Engine Control Module, a computer that controls various engine functions such as fuel injection, ignition timing, and emissions.

ECU

Stands for Engine Control Unit, a computer within a vehicle that controls various aspects of the engine's operation, including timing, air/fuel mixture, and more.

Truck System

A comprehensive arrangement of components and mechanisms which constitute the functionality of a truck, including its engine, transmission, drivetrain, and electronics.