Publisher Summary This chapter explains the operation of the sensors and actuators used throughout a modern car. Special emphasis is placed on sensors and actuators used for power train (i.e., engine and transmission) applications since these systems normally employ the largest number of such devices. The chapter also discusses sensors found in other subsystems on modern cars. Automotive electronics have many examples of electronic control in virtually every subsystem. Modern automotive electronic control systems use microcontrollers based on microprocessors to implement almost all control functions. Each of these subsystems requires one or more sensors and actuators in order to operate. Fundamentally, an electronic control system uses measurements of the plant variable being regulated for feedback control. Temperature is an important parameter throughout the automotive system. In operation of an electronic fuel control system, it is vital to know the temperature of the coolant, the temperature of the inlet air, and the temperature of the exhaust gas oxygen sensor.