Based on the input data and characteristics stored in the microprocessor memory, the ECU calculates the fuel injection time and moment and converts these parameters into output signals that are used to control the fuel injectors. In addition, the output signals are also used to control various components and systems such as the exhaust gas recirculation system drive, fuel pump relay control, radiator fan, engine preheater and air conditioning system. The actuators are protected against short circuits and electrical circuit breaks, and any damage is recorded in the microprocessor memory. Many output signals are used in other vehicle systems.
The greatest load on the ECU output stages is exerted by the fuel injectors. The output stage current creates a magnetic field in the injector solenoid valve, which is applied to the high-pressure fuel portion of the injector. To ensure a precise amount of fuel is injected, the injector opening must occur very quickly, which requires the ECU to supply high voltage. The fuel injector control circuit has two phases: an opening phase characterized by high current consumption, and a holding phase characterized by low current consumption.
The ECU meets high requirements regarding:
- exposure to ambient temperatures within the range of –40...+85°C;
- resistance to fuel and lubricants;
- resistance to moisture;
- mechanical loads.
The ECU also has electromagnetic compatibility (EMC) and has low radiated emissions.