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Your Automobile, Your Pc: ECUs, and the Controller Area Network

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Your Automobile, Your Pc: ECUs, and the Controller Area Network


Previously, a shade-tree mechanic could diagnose and fix his own vehicle with relative ease.


As a child, I spent countless hours working with my father on our own vehicles, switching parts, adjusting timing, altering fuel ratios, working on brakes, you name it. He had been an aeroplane mechanic in WWII and a factory electrician for 32 years.

Even that comprehensive background may not be sufficient today. This type of work necessitates a higher level of technical skill and computer knowledge.

Your car is now more than just a mechanical conveyance; it is a complicated computing system. In fact, your car might have a network of computer nodes connected via a bus network design. The nodes are known as Electronic control units (ECU), and the bus topology is known as the Controller Area Network (CAN) (CAN).


Electronic Control Modules

The word “ECU” refers to equipment that governs electrical systems in modern automobiles. ECUs come in a variety of shapes and sizes, and their functions vary. Some high-end vehicles may contain up to 100 ECUs. These serve a variety of purposes, including engine control.

  • Control of the transmission.
  • Control of the brakes.
  • Assist with speed.
  • Assist with parking.
  • Climate control is automatic.
  • Control of traction.
  • Control of the anti-lock braking system.

Vehicle manufacturers’ terminology may differ. The engine control module (ECM) or engine control unit (ECU) is the ECU that manages the engine (ECU). The use of ECU to refer to either a generic electronic control unit or a specific engine control module might be confusing. The engine control module and the gearbox control module are frequently integrated into one ECU known as the powertrain control module (PCM). Many people consider the ECM or PCM to be the vehicle’s “Central Processing Unit (CPU).”

In reality, the different ECUs installed throughout the vehicle perform distinct functions and serve as individual nodes within the automobile network architecture. And that’s only the start! ( Check out this feature on autonomous vehicles to learn more about the technology available in modern automobiles.(“Are These Self-Driving Cars Ready for Our World?”)then consider how much of this technology is currently included into models coming off the assembly lines!)

Manufacturers have set lofty targets for developing and upgrading car technology. The use of ECUs and related systems has now resulted in a new sea change toward what is known as “lidar” or “laser radar,” in which sophisticated groups of sensors assist the vehicle in “seeing” what is around it in order to implement lane departure warnings, automatic braking, and other features mentioned above.

Car manufacturers are also changing how drivers interface with their vehicles, using biometrics and cutting-edge controls that render steering wheels and key ignitions obsolete.

ECUs automate and implement these process improvements in real time. Multiple sensors receive information from the network and give commands to actuators, which provide the interventions needed to achieve the optimum results. The output of the sensors tells the system what the automobile is doing, and the entry of new instructions corrects the situation. ECUs make use of information provided by sensors such as the:

  • Sensor for engine coolant temperature.
  • Temperature sensor for the air.
  • Absolute pressure sensor with a manifold.
  • The sensor of mass airflow.
  • Controller for idle air.
  • Sensor for the crankshaft.
  • Sensor for the camshaft.
  • Sensor for oxygen.
  • Sensor for knocking.

Analogue-to-digital converters, digital-to-analogue converters, signal conditioners, communication chips, instrument clusters, and smart sensors are all part of an ECU. Analogue information can be transformed into digital representation for electronic processing. All of this data is routed through a bus topology known as a controller area network.

Controller Area Networks (CANs)

This is a digital computer network that communicates with the numerous ECUs located throughout the vehicle. Each ECU node handles information input and output as it communicates with the vehicle’s mechanical and electrical components. Ambient temperature, coolant temperature, airflow, and acceleration position are all processed and activated as fuel injection, ignition timing, and turbo boost, among other things. A constant feedback loop is provided by CAN networks.

The CAN protocol stack can be compared to the two lowest layers of the OSI architecture.

In the CAN model, the OSI physical layer corresponds to three physical layers. In CAN, the data link layer is equal to the logical link control (LLC) and media access control (MAC) levels. More information about the technology can be found in ISO 11898-1:2015 – Road vehicles – Controller Area Network (CAN).

Robert Bosch GmbH introduced the Controller Area Network bus in 1983. A microprocessor, a CAN controller, and a CAN transceiver are all included in each CAN node. CAN is a message-based protocol that employs either an 11-bit (standard) or a 29-bit identifier (extended format with 18 extra bits). The hardware and software (really firmware) components of the CAN bus can be changed and upgraded using extra chips or software commands.

To govern traffic, CAN employ an arbitration procedure similar to CSMA/CD in the Ethernet system. CAN may be complemented inside vehicle technology by alternative technologies such as Flexray, which employs TDMA and runs at up to 10 megabits per second, or Local Interconnect Network (LIN), a single-wire serial network protocol. There has been considerable discussion of replacing Flexray with Ethernet, which would give some significant benefits. CAN bus is one of five protocol standards recognised by onboard diagnostics technology (OBD).

Diagnostics Onboard (OBD)

In 1996, OBD-II replaced the original OBD. Initially intended to manage emissions in order to meet government standards, the newer standard has developed to include a slew of new features. OBD-II, as a digital diagnostic, consults a massive database of codes, which can be found at www.troublecodes.net. P0171, for example, is a generic powertrain code that implies “the system is too lean.” The five-digit codes are written as follows:

[Alpha] – region (Body, Chassis, Powertrain, U – network)

# denotes the manufacturer’s code

# denotes the system

# – troubleshooting

# – troubleshooting

There are several methods for retrieving OBD-II codes from your vehicle. The majority of car parts businesses will bring out a device that plugs into a computer port under your dash. You might also purchase a scanner tool and read the code yourself, as Wikihow explains. With the correct cable, a laptop, and specific software, you can even hack into your car’s computer. Some of the graphic interfaces can reveal a wealth of information about the inner workings of your automobile computer. Just keep in mind that any hacking you undertake is entirely at your own risk and is not encouraged by the automobile manufacturer or this website! (See Cloud Computing for Vehicles: Tomorrow’s High-Tech Car for more information on cloud connectivity in vehicles.)



We’ve already stated that your car is a computer. To be more specific, your car is made up of numerous computers linked together in a sophisticated network. Microprocessors in late-model vehicles may enable complex engine management, enhanced diagnostics, new safety or comfort features, and even wire reduction. The advantages of this cutting-edge car computing are numerous, but some argue that the ease of home auto repair is long gone.

When I was younger and worked with my father, I never dreamed that my knowledge of car repairs could compete with his. Now I’m wondering if my experience as a network engineer will be useful here.

I’m also curious how long it will take for cars to become self-aware, similar to David Hasselhoff’s car KITT in the TV show “Knight Rider.”

You cannot halt progress.


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