Overview??Data Gold Mine Modern vehicles have electronic control units (ECUs) to control various subsystems such as the engine@ brakes@ steering@ air conditioning@ and infotainment. These ECUs (or simply ??controllers??) are networked together to share information. This information is a potential data gold mine for the data acquisition user. Figure 1.1 shows an example of ECUs on a typical truck in-vehicle network. Each controller has its own data acquisition system which consists of sensors@ signal conditioning@ an analog-to-digital converter@ and processor. Each controller outputs directly measured and calculated data to the network to communicate with otherother controllers. The number of controllers varies across vehicle models. Ten controllers are common on an HD truck@ while some luxury cars are approaching 100 controllers. Here are the major functions a typical engine ECU performs: 1. Digitization of sensor data in real time 2. Interpretation of the sensor data 3. Adjustment of its actuators in real time for optimal air?Cfuel mixture@ ignition timing@ idle speed@ etc. An ECU consists of both hardware and software (firmware). The acronym ECU is used by some to designate the engine control unit. We will use ECU for electronic control unit only@ meaning that it can refer to any controller on the vehicle.