Technician Handbook ! 673 Electronic & Computer Controlled Systems How ECUs Work An ECU is a small computer programmed to perform a specialized function in the vehicle. As with any computer, it operates on the principle of input, processing, and output. Input – Information about conditions is supplied to the ECU as input signals. Input can be provided by: • Sensors • Switches • other ECUs. Processing – The ECU analyzes the input signals. Based on its programming, it determines what output signals to send, if any. Output – Vehicle systems are controlled by the ECU output signals. These signals may cause a motor to operate, a light to come on, or some other operation of a vehicle component.
Logic Function For an example of the ECU’s logic function, consider the lighting control system which is within the Body ECU. A simple lighting control system uses three inputs – the light control switch, the light control sensor, and the ignition switch. When the condition of these three inputs matches the conditions preprogrammed in the ECU, the ECU turns on the headlights and taillights. Technical Training 7