21st Century - Sensors & Diagnostics

The invention of the microprocessor was soon applied to car onboard diagnostics.   There are several computers on a modern car.   The Society of Automotive Engineers (SAE) calls the engine controlling unit the Powertrain Control Module (PCM).   It monitors and changes car functtions as required.   It consists of one or more circuit boards installed in a metal case to prevent electromagnetic interference (EMI).   Wire harnesses connect the computer with sensors and actuators located at various points in the car.   The PCM is located in the engine compartment where it is cooled by air from the radiator fan.   The computer need not respond to data from any sensor, nor respond to data in just one way.   It may ignore data or respond in different ways to the same data depending on inputs from several sensors. ^{Halderman 595} Diagnostic Detail provides more technical information on how the computers and sensors operate. operate.