Optical sensors may use infrared Light Emitting Diodes to peer through a slotted wheel. Other sensor designs interpret the rise and fall of magnetic energy as a metallic part approaches and departs. Other data signals are critical to powertrain control. The microcontroller has to know temperatures in the engine's water cooling system along with oil temperature and transmission temperature. Fuel injection requires knowing atmospheric density and how quickly air is being drawn into the intake manifold.
Air temperature affects air density.
Hydraulic pressure information is sent to the microcontroller by automatic transmissions, as are battery voltage, road speed, and oil pressure. Every signal adds calculation complexity as it increases the precision of control. The precise management provided by digital control means every automatic transmission will soon be under numeric control. As engine control advances, so does data complexity. Oxygen sensors enabled controllers to accurately mix air and fuel based on combustion results.