Based on the input data and characteristics stored in the memory of the microprocessor, the ECU calculates the time and moment of fuel injection 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 elements and systems, such as the EGR actuator, fuel pump relay control, radiator fan, engine preheater and air conditioning system. The actuators are protected against short circuits and open circuits, and any damage is recorded in the microprocessor memory. Many output signals are used in other vehicle systems.
The fuel injectors put the most stress on the ECU output stages. The output stage current creates a magnetic field in the injector solenoid valve, which is applied to the high pressure fuel part of the injector. To ensure the correct amount of fuel injected, the injector must open very quickly, which requires high voltage from the ECU. The fuel injector control circuit has two phases: an opening phase, which consumes a large current, and a hold phase, which consumes a small current.
The ECU meets high requirements regarding:
- exposure to ambient temperature within -40...+85°C;
- resistance to fuel and lubricants;
- resistance to moisture;
- mechanical loads.
The ECU also has electromagnetic compatibility (EMC) and has a low level of radiated interference.