Before the advent of computer controlled engine management systems, the source of many auto malfunctions was something you could see. Pop off the distributor cap and you could see burned or closed points, carbon tracks that would cause a misfire or a cracked cap or cracked rotor. You could look down the throat of the carburetor and observe the fuel flow and atomization. A simple compression test revealed a lot of information about the mechanical condition of the motor. Altogether there were not many parts involved in the operating system of the engine; just a distributor, spark plugs, ignition cables and a carburetor.
Beginning in the late 1970s in order to meet federal emission and fuel economy standards manufacturers began to add electronic controls and sensors to the fuel and ignition systems. In 30 years electronic controls have evolved and expanded exponentially. Now electronic management is thoroughly integrated into most systems. Engine controls, transmission controls, antilock brakes, traction control, air bags, automatic climate control and collision avoidance systems are present in today’s vehicles and the number of sensors and operating devices number in the hundreds.