Electronic control systems in a modern vehicle is reponsible for monitoring and managing engine functions. these functions used to be performed by mechanical components, such as a carburetor. System elements are placed in order for proper monitoring and management of the engine functions, they are Input sensors, a Microcomputer (ECU), and output actuators.
The input sensors allows the ECU to monitor engine operating conditions, utilising data gathered from the input sensors. EG. an idle speed control allows more air to flow through for easier cold start.
When the ECU receives information from the Input sensors that a change is required, the ECU controls a set of actuators to achieve the desired change. To operate an actuator, the ECU relies on a component called a "output driver". Output drivers are nothing more than a specific on and off switch to control the actuator.
An example of the relationship between input sensors and output actuators is the Throttle position sensor (TPS). as the TPS increases, the fuel injector sprays more fuel into the combustion chamber to increase the RPM of the engine.
The heart of the emmisions control system is the closed loop fuel control feedback system. its reponsible for controlling the content of gases from the catalytic convertor and decides how much the feed gases (HC, CO and NOx) leave the tail pipe. the oxygen Sensor, also called a “lambda sensor” is detect the oxygen content in the exhaust gases as they pass from the engine. the amount of oxygen going into the engine is a measurement of the air to fuel ratio of the mixture going into the engine.
The oxygen sensor feeds the ECU with information, the ECU then adjusts the fuel injection pulse width (spray time length) with the injectors. this process is continous, so there should be optimal air to fuel ratio. If a input sensor is bad, then there will be a incorrect air to fuel ratio.
