Most vehicles usually have more than one ECM (electronic control module). An engine control unit (ECU) can be called the ECM governing the engine control functions. An ECU processes various input information based on different factors (engine temperature, engine speed, accelerator pedal position, fuel grade etc) to control fuel and ignition systems, while improving fuel economy with low emissions. Thus, you can say that an ECU works to assure ecological and economical engine operation.
An engine control unit is made up of several functional blocks which are as follows:
- Power Supply – it usually is DC-DC converter where the battery voltage gets converted into voltage levels suitable for the digital circuitry and the MPU. However, in some cases, it can provide power for the analog sensors.
- MPU – this consists of the microprocessor and memory (typically, RAM and Flash)
- Communications Link – it helps in transmitting engine control data from or to the engine control unit.
- Discrete Inputs – these inputs are on/off switch types.
- Analog Inputs – they feedback the signals from sensors.
- Frequency Inputs – these are encoder type signals (for example, vehicle or crank speed)
- Switch Outputs – these are on/off switch types outputs.
- PWM Outputs – often considered to be the most complicated outputs of the engine control unit, they help maintain duty cycle and variable frequency, in addition to controlling fan speed.
- Frequency Outputs – they help maintain constant duty cycle (for example, idle speed control by stepper motor)
Now that you know about the functional blocks of engine control unit, you should keep a close eye on them to make sure that your engine is performing at its optimum. Remember that while controlling your car’s engine is the most processor-intensive task, the engine control unit is its most powerful computer that can ensure its proper functioning.




