Electronic Control Unit (ECU)
ECU which is Electronic Control Units, these are all the Control Units in the car. It means all the system which has the control over various sensors in the vehicle.
Before I continue on ECU, let me talk about Sensors.
Sensors are electrically devices that send electrical signals from various components of the vehicle to the computer inbuilt in the car (ECU) whenever such system is not in normal working condition.
Sensors are located in almost all parts of the car, old cars used to have sensors in the Engine and Transmission, but modern cars have in all parts including wheels, lights, doors, body, seats and more.
The more the sensors the more electronics system in the car, that is why almost all parts of modern cars have electrically connections and devices.
These sensors send signals to the ECU; each sensor signal is unique as it is interpreted as a code (fault code) which brings us back to the previous lessons. Also each component that has a sensor also has its own code.
This quality of interpretation (i.e. information) of signals provided by the diagnostic tool is what makes a diagnostic tool superior to others.
The diagnostic computing system (I.e. ECU) receives signals through Controller Area Network (CAN) and processes it for interpretation for a diagnostic tool.
Now back to ECU, the size of the ECU depends on the numbers of System (group of components that works together to perform a single function) in the car. Old cars can have about fifteen Control Units, but modern cars can have up to ninety Control Units. Examples of control unit are Transmission, Motor Electronics, Telematics, Fuel pump, etc.
Controller Area Network (CAN)
The CAN is a system that helps to control and aid communication between the ECUs. It helps to send message to the ECU. The CAN is responsible for features like PARKING ASSIST; this is when a sensor at the body of a car senses a close by object increases the Braking of the car.
It is also responsible for proper communication and responses of various Actuators and ECUs, such as ABS, ESP, SRS, and other systems in the vehicle.
When signals is not received by the CAN or when the CAN doesn’t send signals, the diagnostic system would not be able to determine the state of the actuators or systems.
You are going to find the term CAN, often when you engage in Diagnostics.
One day at the workshop I was diagnosing a vehicle with an MB C4 Star and on checking a control unit (AC compressor), I could not detect an exact fault, and the AC system was not working properly. On checking further I discovered that the CAN was not receiving signals from one of the components on the AC system. We had to trace the bad fuse causing the open circuit and replace it. Then the AC system started working properly.
There is also a signal control system in the vehicle known as SIGNAL ACQUISITION MODULLE (SAM), this is also a computerized system that helps acquire signals from various sensors in vehicles especially in modern vehicles with complex electronics and mechatronics system. This to
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