After, we had the oxygen sensors (the popular lambda probe), able to measure the amount of oxygen in the exhaust. With the signal from this sensor, the ECU can “learn” whether the mixture is poor or rich, and make the adjustment by sending differentiated signals sent to injection valves and electronic butterflies.
These primitive plants were a major breakthrough against the carburetors but they still could not compensate for the higher density of air on the coldest days. With the evolution, the electronic injection systems began to adopt more sensors of the entrance to allow better management of the motor. Air temperature sensors, for example, allowed the ECU to send a different signal to the injection valves on cold days (increasing the injection time to enrich the mixture). Then came the coolant temperature sensors, which went on to tell the ECU whether the engine was hot or cold, further optimizing engine management.
As you may have guessed, it all started as a system that used two input sensors and a single actuator that received the output signal from the ECU and evolved into something much more complete, which incorporated rotation sensors, detonation, and throttle. That was still only the beginning.
ECU = Electronic Control Unit
Technological evolution has allowed a drastic increase in information processing capacity, which in turn has allowed the creation of new management systems not only of the engine but also of other car systems. The replacement of mechanical instruments with electronic instruments, for example, has transformed the instrument cluster into an electronic module, which processes the signal sent by the engine ECU and sends it to the speedometer, gauge and fuel level marker. Did you notice that for the first time in this text I called the engine ECU? It is because this electronic panel is considered an electronic control unit, which is the acronym in English is also known as ECU or Electronic Control Unit.
The anti-lock braking system, ABS, is also based on an ECU: rotation sensors send a signal to an electronic control unit. If the rotation of one or more wheels is interrupted, the ABS ECU sends a signal to an actuator that relieves the hydraulic pressure of the tongs intermittently to prevent wheel locking.
Like the engine-ECU, the ABS-ECU also evolved to integrate more sensors and actuators and from this
evolution emerged the electronic brake distribution, capable of acting only on the locked wheel and no longer on the whole system.
From this technology also emerged the electronic controls of traction and stability: if the speed sensors and actuators controlled by an ECU can prevent the wheels from braking, they can also monitor and control the difference in speed between them, something that would indicate a distraction in certain circumstances.
Also, as the engine-ECU added the ignition to better manage engine operation, integration of the ABS/EBD, ECU and the traction and stability controls with the engine-ECU, allowed a much more precise and efficient management of these auxiliary systems, conditioning them to the speed, position of the wheels, angle of the steering wheel, and basing its operation not only on the braking performance but also on the ignition, injection cut and the closing of the butterfly (to understand better, read our complete post on the operation of these systems).
In addition, other electronic systems of cars over time have gained their own modules as a way to reduce the heavy tangle of wires known as an electric whip. For example, the digital air-conditioning is an electronic module (ECU) that receives the temperature sensor signal to determine which fan speed and which temperature of the blown air will be required to obtain the desired temperature by the occupants of the car.
Door Module in an Audi
In more sophisticated cars, even the doors have their own control modules as a way to simplify the circuits and reduce the weight generated by electric wire pairs. Imagine a car with electric locks, power windows with an anti-fog system and door suction system. All of this can be operated by a “door-ECU”, which receives signals from other ECUs – or from its own sensors – and sends signals to actuators of the door on which it is installed.
The Interconnected ECU Networks
Today modern cars can have up to 70 different ECUs – and most of them communicate with one another through a standard called CAN bus (Controller Area Network), an intercommunication protocol between control modules that is independent of a central server.
With so many interconnected ECUs, the name “ECU” in the automotive application fell into disuse and was replaced by more specific acronyms. The engine-ECU, for example, is now better known as “ECM” (Engine Control Module). The door module quoted above is the Door Control Unit (DCU).
When the car uses an electronic automatic gearbox, it usually uses a Transmission Control Module (TCU). Currently, the TCU is integrated with the ECM to form the PCM or Powertrain Control Module. The cruise control (adaptive or not) and the speed limiter also have their own module: the SCU or Speed Control Unit. Hybrid and electric cars use a battery management module, the Battery Management System while the traction control, stability, ABS and EBD systems, and brake-based torque vectoring are controlled by the Brake Control Module (BCM).
