Jump to content

  • Welcome to Auto Parts Forum

    Whether you are a veteran automotive parts guru or just someone looking for some quick auto parts advice, register today and start a new topic in our forum. Registration is free and you can even sign up with social network platforms such as Facebook, X, and LinkedIn. 

     

All Aboard the CAN Bus


Recommended Posts

rssImage-aaf284e38f7b16a7b9541979751e43ad.jpeg

One of the more difficult things about any technology is all the new terms you seem to get hit with, and in the automotive world, CAN bus was one of those terms. The second half, “bus,” was a term we had already used for many years, primarily as “bus bar.” A bus bar was a metal strip or bar that distributed power among multiple components.

In the automotive world, even when fiber-optic turn-signal indicators mounted on the front of a fender were as high-tech as it got, bus bars were inside many components such as fuse panels and relays, and sometimes under the hood for various engine electronics.

Then computer electronics took over. At first, we just had one electronic control unit (ECU) to deal with, and it was for the engine. Before you knew it, there was a transmission control unit, then the ABS control unit (not necessarily in that order). Wiring harnesses got bigger … and bigger and bigger.

Today, a car can have as many as 150 ECUs. In addition to the familiar engine, transmission, brake and airbag control units, doors, seats, mirrors, power steering, audio systems, cruise control, batteries and charging management systems all have their own control units. And as you can imagine, that’s just scratching the surface.

As technology was taking a ride with all these systems, engineers realized there were too many wires and too many sensors. There was no choice but to get aboard the CAN bus. CAN stands for controller area network, and a CAN bus, simply put, is a common communication line that can be used by all ECUs on the network.

The various control units on a modern vehicle need to communicate and share information over this network. Here’s an example of how and why. Years ago, when you turned on the air conditioning, a simple switch sent power to the compressor clutch. Today, the HVAC control module may need to communicate with the body control module (BCM) to notify it that A/C has been requested.

The BCM in turn sends a request to the engine control module (ECM) to “ask permission” if it can energize the A/C-compressor relay. The ECM looks at current engine operating parameters and sends a response signal to the BCM, which, in turn, sends a signal to the A/C relay.

The technological features on today’s cars are nothing short of impressive. Advanced driver-assistance systems (ADAS) include features such as adaptive cruise control, forward collision warnings, high-beam safety, lane-departure warnings, traffic-signal recognition, lane-keep assistance, automatic emergency braking and traction control.

All of the associated control units are in constant communication with each other, and since many of them must utilize information from the same sensors, through the CAN bus network this is possible. Instead of an ambient-temperature sensor for the ECM, the HVAC control unit and the instrument cluster, one sensor can share its data over the network.

Some high-end vehicles have a feature called automatic brake wiping, or brake disc wiping. This feature utilizes information from a rain sensor (also used by automatic windshield wipers) that’s sent over the CAN bus to the ABS control unit. In programmed intervals, the ABS control unit lightly applies the brakes in a manner that the driver won’t notice, to clear water and moisture away from the rotors and provide maximum braking when needed. All of this is only possible thanks to the communication available over the CAN bus.

Developing the CAN bus system was no simple feat, and it took many years to complete. The requirements for automotive CAN bus communication are standardized as part of the OBD II vehicle communication standard. There have been many changes over the years related to CAN communication, primarily affecting the speed and manner in which data is transmitted. The easiest way to think about it is to relate it to the changes over the years in USB design we’re all familiar with. It’s for the same reason. They transmit data quicker.

From a service standpoint, technicians have had to become familiar with CAN bus systems. U-codes that indicate a loss of communication between modules or on a specific bus are a tool designed to help technicians diagnose CAN bus problems.

Electrical wiring diagrams reflect the CAN bus network, and there are three different types of networks – loop, star and loop/star hybrid – referred to as CAN bus topology. Being able to recognize the type of topology can help a technician diagnose CAN bus errors quicker. In today’s world, we all have to get aboard the CAN bus.

The post

link hidden, please login to view
appeared first on
link hidden, please login to view
.

link hidden, please login to view

Link to comment
Share on other sites

Great Tire Deal

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Topics

    • By carbdoc
      I cannot find a remanufactured brake booster for my 1978 Dodge D-150 truck with 400 c.i.d. engine to save my life!  Yes, I can send mine out for rebuilding and hope that it comes back correctly repaired (or comes back at all), but I don't want to take my truck completely out of service while I wait for it to (hopefully) be correctly rebuilt.  I would, however, gladly settle for a "loose" rebuildable core.  

      If anyone reading this has a rebuildable core that they will sell to me, I would be quite grateful.

      Jeff
    • By Dorman Products
      Don't make this common oil catch can mistake
    • By Dorman Products
      Technicians vs. DIYers: How well can you gauge tire pressure?
    • By NAPA
      Chase Elliott and the No. 9
      link hidden, please login to view team started 15th in Sunday’s NASCAR All-Star Race at North Wilkesboro Speedway after Saturday’s heat races were rained out and the lineup was set by qualifying results. When the first caution flag of the race came out on lap two, Elliott was scored in the same position in which he started. Under the yellow, crew chief Alan Gustafson called the 2020 NASCAR Cup Series champion to pit road for the primary tire option after starting the race on the soft tire option. Elliott restarted 16th on lap 11 and found himself inside the top 10 for the first time of the race on lap 41. The Dawsonville, Georgia, native battled with the ninth-place driver for several laps, but he couldn’t make the pass before the scheduled lap-100 caution occurred. The field came to pit road for mandatory pit stops, with the No. 9 team opting for the soft tires it had on earlier in the race. A fast, four-tire stop by the NAPA Racing crew gained Elliott two spots on pit road, and he lined up eighth for the choose cone, taking the inside lane for the restart on lap 109. The Hendrick Motorsports driver continued to battle inside the top eight and was scored in the seventh position when an on-track incident brought out the yellow flag on lap 118. Staying out on the track under the caution, Elliott lined up on the inside lane for the lap-124 restart and was running in the ninth spot when the second scheduled caution slowed the race on lap 150. Elliott relayed that his NAPA Auto Parts Chevrolet Camaro ZL1 needed more security, so the team made a chassis adjustment during its pit stop for four soft tires and fuel.
      With some teams opting to pit for only two tires, Elliott lined up 12th for the choose cone and took the inside lane for the restart on lap 159. From there, he pressed forward and moved back into the top 10 on lap 165. He managed to gain two more positions before the checkered flag waved, claiming an eighth-place result in the 200-lap all-star event. It was Elliott’s second consecutive top-10 finish in the exhibition event and seventh top-10 overall in nine All-Star Race starts, which includes his 2020 victory at Bristol Motor Speedway when he took home the $1-million prize.
      Start / Finish: 15 / 8
      Points Standing / Total: 4th / 437 pts. (-49)
      Next Race: Sunday, May 26, Coca-Cola 600, Charlotte Motor Speedway
      How to Watch or Listen: 6:00 p.m. ET on FOX, PRN and SiriusXM
      NAPA: 
      link hidden, please login to view
      Chase Elliott:  link hidden, please login to view
      Hendrick Motorsports:  link hidden, please login to view
      No. 9 Team:  link hidden, please login to view The post
      link hidden, please login to view appeared first on link hidden, please login to view.
      link hidden, please login to view
    • A-premium Auto Parts:5% OFF with Code GM5.
    • By celvampire
      I found what looks to be an unused O2 sensor found in a thrift store, there are no marking anywhere on the part. Can anyone tell just by looking at it, what car/truck it might fit? Thank you.





×
  • Create New...