Microprocessors, Sensors, and Voltage-Generating Devices

Microprocessors or central processing units (CPUs) are programmable devices that are found in vehicle ECUs. They are computers that monitor information from inputs such as sensors and make decisions based on their program, then output signals to actuators and electrical devices on the vehicle. Microprocessors control and monitor most electrical systems on the modern vehicle. For example, there are microprocessor control units for the engine, transmission, suspension, brakes, steering, and main body control functions. Modern diagnostic equipment connects into the microprocessors on the vehicle via a data link connector to provide information on system performance to the technician. It is not unusual for the microprocessors on a vehicle to require programming updates. Updating is performed by reflashing or reprogramming the memory in the microprocessors with an update supplied by the manufacturer.

There are many different types of sensors installed into the modern vehicle, and they are used to provide information to the microprocessors on the vehicle. A sensor essentially converts a mechanical action into electrical signals that can be read by the microprocessors in the control units. For example, the sensor installed near the crankshaft converts the rotary movement of the crankshaft into electrical signals that tell the microprocessor each time the crankshaft has rotated through a certain number of degrees and where it is in relation to top dead center of a cylinder, typically cylinder 1. The temperature sensor converts the temperature of the engine coolant into an electrical signal that can be read by a microprocessor.