Operation General The ECM controls the operation of the engine using information stored in its memory in the form of maps. The maps contain data which is used to determine the most efficient fuelling for any given driving condition. The ECM also has maps for the operation of subsystems such as EGR. The ECM is an adaptive unit which learns the characteristics of the vehicle components. This feature allows the ECM to compensate for any variations in components fitted to the vehicle in production, and to adapt to changes of components which may occur in service. The ability to compensate for 'wear and tear' and environmental changes during the life of the vehicle ensures that the ECM can comply with emission control legislation overextended periods. The ECM is programmed with a 'strategy' which controls the decisions about when to turn specific functions on and off. The inputs to this decision making process are supplied by sensors, mounted at various locations on the vehicle, which supply information to the ECM. If a sensor fails to supply information, the ECM, where possible, will use data from other sensors and use a default value for the missing information. In cases where default values cannot be used, the vehicle will be disabled. Use of a default value may result in reduced performance, increased fuel consumption and exhaust emissions. The ECM is programmed with vehicle specific information known as 'calibration. This data is used to calculate ECM outputs. This information, together with data inputs from sensors and other system ECU's, determines output signals from the ECM to the actuators. The ECM uses strategies such as: l Smoke limitation l Active surge damping l Automatic gear change l Fuel reduction l Engine cooling l Combustion noise limitation. During idle and wide open throttle conditions, the ECM uses mapped data to respond to the input signals from the APP sensor. To implement the optimum fuelling strategy for idle and wide open throttle, the ECM requires input data from the following sensors: l CKP sensor l APP sensor l ECT sensor l MAF/IAT sensor l Fuel rail pressure sensor. This data is then compared to mapped data within the ECM to control acceleration using the following actuators and controllers: l EGR modulator – closed for cleaner combustion l Fuel pressure control valve – increase fuel pressure supplied to fuel rail l Electronic fuel injectors – change injector duration l A/C compressor clutch relay – de-energised during wide open throttle to reduce engine load l EAT ECU – kickdown activation. During cold start conditions, the ECM uses ECT sensor data to determine if the cold start strategy is required. During cold start conditions, the ECM will inject more fuel into the cylinders and will initiate the glow plug timing strategy for effective cold starting. Normal fuel strategy is used during hot starts.