This document discusses electronic control units (ECUs) and engine management systems (EMSs) for vehicle engines. It lists common sensors used in EMSs, including primary sensors like the manifold absolute pressure (MAP) sensor and mass air flow (MAF) sensor. It describes the functions of control systems in different stages and standard ECU modules like the powertrain control module. It outlines the advantages of ECUs/EMSs and features like onboard diagnostics. It also discusses auto tuning through reflashing the ECU software map.