Jump to content

CAN systems


Recommended Posts

I'm working on a "requested" article from one of the magazines I write for. They want an article on CAN systems (Controller Area Network) I need some feedback as to what you think of this article. I have several different ideas on how to simply the workings of a CAN system, but this one seemed the most "overall" explanation of it. Your reply and ideas is greatly appreciated.


Can do CAN:

A simple look at a complex system: Controller Area Network: CAN


Ever wonder how your cable TV comes into your home on that single coaxial cable? In simple terms… it’s like a CAN system. A good definition of a CAN system would be: High speed communication sent via data lines to and from components. Just like your cable TV, as a signal is sent down the wire from one communication device there needs to be another at the other end that can “descramble” that information and turn it into readable information. These “lines” are generally referred to as BUS lines, or Data lines.


Most of the time they are in pairs of two wires that are twisted together (less RF interference). Some manufacturers use a 2 speed CAN. One line is for low priority information such as radio, windows, etc… and a faster 2nd speed for things like transmission, theft, etc… both system moves along the same wires at the same time. What each of the “modules” that are on the BUS line do is only use the information that they are programmed to read all else is just ignored and not read by that particular module.


What to expect:

The direction of these CAN systems are not going to go away, they’re with us for now and most likely even more complicated in the future. Scanning is the key to working with these systems. Proper scanners and not just a “code reader” is the necessary tool to see these “TV” channels on your little screen (your scanner). A dealer equivalent scanner is the best way to “look” at these systems. Mode $06 is another option but one thing you don’t want to do any more is stab a wire with a test light looking for current or ground… it ain’t there.


Imagine stabbing your test light into your cable TV line. What do you think you would find there, nothing that a test light would help with. Also, I don’t advise sending voltage or a solid ground down a data line. Would you try that with that coaxial cable coming into your house, I think not..! My advice when it comes to diagnosing power windows, gauges, or for that matter just about anything these days. Get your scanner out and look for codes, look for a class 2 serial data line on your GM, read the mode $06 information, and or whatever that particular manufacturer is calling their CAN line information. These data information screens will give you the clues as to what to be looking for. The next stop is to your PC and look up the wiring diagrams. Codes are only a starting point; remember… you still have to diagnose the cause of that code and what it means.


Here is an example:

03 Cadillac DHS

If you used the driver’s side window switch the driver’s window and the passenger front window would go down simultaneously and would go up the same way. If you tried the front passenger window switch nothing happened at all. The driver’s side rear window switch from the driver’s door switch if pushed would operate both the rear windows exactly like the front set. The car was clean, well kept and had no signs of any recent damage. As far as the owner knew there was nothing out of the ordinary that might hint at a possible reason for this strange window fiasco.


Scanning the car led to several history codes that could be related and some codes that couldn’t be related to the problem, that is until I went to the class 2 serial data line information. It listed where the trouble was at… corrupted information and loss of communication on the BUS. Looking at the four door modules showed that the scanner couldn’t communicate with either passenger side modules. Using the scanner to operate the windows without having to move the switches showed no difference between the scanner and the actual window switch from the driver’s door. Pulling the prints showed that the serial data lines ran from door to door and back to the BCM. There were no obvious wiring issues to be concerned with but I did notice several slight whitish droplets dried onto the inside of the door. It looked to me like “Bondo” or sanding dust mixed with water. But the owner knew nothing of any body work ever done to the car. Opening the FPDM and examining the circuit board showed no water damage. With the data lines showing no communication with the modules and the wiring looking perfect the next best thing was to change the FPDM and RRDM (Front Passenger Door Module, Right Rear Door Module).


It worked like a charm. After replacing the modules I went back into the scanner to see if the communication had been restored, sure enough it was… another job out the door


I never picked up a test light like I would have on an older car and I didn’t have to pull out the old trusty tap hammer and start banging around till something moved. Using the scanner and the CAN lines showed where to go to make the repair.


History lesson:


1983 Bosch Corporation introduced the CAN system to the world as a preparation to what they saw as an increase in the automotive electrical system advancements. In 1987 the first CAN system was officially called “CAN” but it wasn’t till 1992 Mercedes Benz that a CAN system was accepted as the true first CAN system. Early GM’s had a system that could have been called CAN back in 1987 but the only references were to call the lines “data lines”. It still worked about the same way but wasn’t diagnosed the same way as we do today.


1995 GM introduced Class 2 serial data lines which run at a speed of 10.4 kbps. In 2004 Gm went to their next generation system called GMLAN (local area network) which had a 2 speed system: low 33.3 Kbps and a high at 500 Kbps. Mercedes Benz uses several BUS lines; on one car I counted 5 different CAN speeds.


Closing: With the speed and flexibility of these electronic systems the manufacturers can create in today’s cars I can only imagine how far all this information is going to go. It could be at some point in time that wiring will be a thing of the past too. Everything in the car could someday go completely wireless; modules will get smaller, faster and less likely to failure. Scanning could be done without even seeing the car in a repair shop. Just dial your cel phone to your shop of choice and a complete diagnostics could be done right then.


I know it sounds a little “out there” but just imagine what a mechanic from the 50’s would think of today’s cars.

Gonzo 2010

Link to comment
Share on other sites

Gonzo you did a good job. May I also congratulate you for reaching 100 in posts on this forum. I am glad you have came along you have added experience, knowledge, and laughs.

I appreciate that... 100 aye? No wonder I've got sore fingers...


I've got plenty more ... as long as I'm not boring everyone... I'll keep it up... thanx-a much-a Gonzo.

Link to comment
Share on other sites

Gonzo, 100 posts in a short period of time! A world of thanks for you valuable contributions!



Thanx, just doin' my part.... glad to do it.

I want to clarify one subject in the story for all you techie guys out there. Mode $06 is mainly for emission systems.. BUT there is some CAN on it... it does not (at this point) talk to any body controlled systems... Gonzo

Link to comment
Share on other sites

  • 4 weeks later...

Here's the printed version for Babcox.

Leave a comment at the bottom of the article if you'd like.


The last part of the article is not mine... it's from Identifix

I hate to tell the author of the article that I fix this problem all the time... it's the crank sensor... crank sensor grounds the tach lead and the BCM picks it up as if the engine isn't running so it will not turn the dash on... see this all the time at my shop.



Link to comment
Share on other sites

  • Have you checked out Joe's Latest Blog?

      Auto shop owners are always looking for ways to improve production levels. They focus their attention on their technicians and require certain expectations of performance in billable labor hours. While technicians must know what is expected of them, they have a limited amount of control over production levels. When all factors are considered, the only thing a well-trained technician has control over is his or her actual efficiency.
      As a review, technician efficiency is the amount of labor time it takes a technician to complete a job compared to the labor time being billed to the customer. Productivity is the time the technician is billing labor hours compared to the time the technician is physically at the shop. The reality is that a technician can be very efficient, but not productive if the technician has a lot of downtime waiting for parts, waiting too long between jobs, or poor workflow systems.
      But let’s go deeper into what affects production in the typical auto repair shop. As a business coach, one of the biggest reasons for low shop production is not charging the correct labor time. Labor for extensive jobs is often not being billed accurately. Rust, seized bolts, and wrong published labor times are just a few reasons for lost labor dollars.
      Another common problem is not understanding how to bill for jobs that require extensive diagnostic testing, and complicated procedures to arrive at the root cause for an onboard computer problem, electrical issue, or drivability issue. These jobs usually take time to analyze, using sophisticated tools, and by the shop’s top technician. Typically, these jobs are billed at a standard menu labor charge, instead of at a higher labor rate. This results in less billed labor hours than the actual labor time spent. The amount of lost labor hours here can cripple a shop’s overall profit.
      Many shop owners do a great job at calculating their labor rate but may not understand what their true effective labor is, which is their labor sales divided by the total labor hours sold. In many cases, I have seen a shop that has a shop labor rate of over $150.00 per hour, but the actual effective labor rate is around $100. Not good.
      Lastly, technician production can suffer when the service advisors are too busy or not motivated to build relationships with customers, which results in a low sales closing ratio. And let’s not forget that to be productive, a shop needs to have the right systems, the right tools and equipment, an extensive information system, and of course, great leadership.
      The bottom line is this; many factors need to be considered when looking to increase production levels. While it does start with the technician, it doesn’t end there. Consider all the factors above when looking for ways to improve your shop’s labor production.
  • Similar Topics

    • By carmcapriotto
      How can different personality types impact leadership and success in business? Murray Voth discusses the importance of understanding personality types in business. He introduces a new acronym, CASE, which stands for Controller, Analyzer, Socializer, and Entrepreneur. The conversation also covers the role of human motivation, clear expectations and accountability in managing employees, and the importance of giving space to your partner in a marriage and how it applies to business relationships. Find out how you can create a harmonious and productive team dynamic, where individuals can play to their strengths and contribute effectively to the business. Murray Voth, RPM Training. Listen to Murray’s previous episodes HERE Show Notes
      CASE: Controller, Analyzer, Socializer, Entrepreneur Defaulting to Personality Types Under Stress (00:08:42) Discussion on how individuals default to certain personality types under moments of stress, fear, and overwhelm. Understanding and Utilizing Different Personality Types in Leadership (00:09:45) Exploring how different personality types, such as controllers, analyzers, socializers, and entrepreneurs, can contribute to effective leadership and business success. Using the SOAR Acronym for Problem-Solving (00:16:19) Introduction of the SOAR acronym (Situation, Outcome, Action, Results) as a tool for problem-solving and decision-making in coaching and personal development. The Outcome and Visualization (00:17:08) Discussing the importance of imagining the desired outcome and visualizing the qualities and skills of a potential service advisor. Taking Actions (00:17:57) Exploring the necessary actions to achieve the desired outcome, such as creating an advertisement, conducting interviews, and ultimately hiring a service advisor. Dopamine and Accountability (00:18:51) Highlighting the role of dopamine in motivating and rewarding oneself throughout the process, as well as redefining accountability as providing clear expectations and tools for employees. The technician who is a serial or the visionary (00:25:22) Discusses the different types of technicians and how to effectively utilize their skills and strengths in a shop environment. The analyzer technician who spends excessive time diagnosing (00:26:17) Explores the reasons behind why some technicians feel the need to overanalyze and prove themselves, and shares a personal story about an apprentice. The importance of decision making and understanding personal strengths (00:30:46) Highlights the impact of decision making on business and personal life, and emphasizes the importance of making decisions based on strengths rather than getting stuck in analysis paralysis. The Growth Mindset vs Fixed Mindset (00:35:20) The concept of growth mindset vs fixed mindset and how it affects learning and personal development. Fear of Regret (00:37:43) The fear of regret and how it holds people back from making decisions and taking risks. The Check Engine Lights of Your Business (00:41:46) Teaching business owners to diagnose their business using KPI technology and scanning tools. Learning How to Learn (00:42:31) Beta testing the idea of using personality assessments to understand team dynamics and improve business performance. Playing to Strengths in the Shop (00:43:36) Positioning team members based on their strengths, such as having analyzers in the background and socializers at the front counter. Thanks to our Partners, AAPEX and NAPA TRACS Set your sights on Las Vegas in 2024. Mark your calendar now … November 5th-7th, 2024. AAPEX - Now more than ever. And don’t miss the next free AAPEX webinar. Register now at http://AAPEXSHOW.COM/WEBINAR NAPA TRACS will move your shop into the SMS fast lane with onsite training and six days a week of support and local representation. Find NAPA TRACS on the Web at http://napatracs.com/ Connect with the Podcast: -Follow on Facebook: https://www.facebook.com/RemarkableResultsRadioPodcast/ -Follow on LinkedIn: https://www.linkedin.com/in/carmcapriotto/ -Follow on Instagram: https://www.instagram.com/remarkableresultsradiopodcast/ -Follow on Twitter: https://twitter.com/RResultsBiz -Visit the Website: https://remarkableresults.biz/ -Join our Insider List: https://remarkableresults.biz/insider -All books mentioned on our podcasts: https://remarkableresults.biz/books -Our Classroom page for personal or team learning: https://remarkableresults.biz/classroom -Buy Me a Coffee: https://www.buymeacoffee.com/carm -The Aftermarket Radio Network: https://aftermarketradionetwork.com -Special episode collections: https://remarkableresults.biz/collections      
      Click to go to the Podcast on Remarkable Results Radio
    • By carmcapriotto
      Join Matt Fanslow as he answers some questions from his listeners in his 'mailbag.' Matt discusses the hiring bonus dilemma, compensation and profit sharing, the power of training, the flat rate pay system, book recommendations and how to create a network of industry peers.
      Have a question for Matt to answer? Email him at: [email protected]
      Show Notes
      Hiring Bonuses for New Techs (00:02:27) Discussion on the fairness and impact of hiring bonuses for new technicians and how it affects existing employees. Broken System of Compensation (00:04:58) Exploration of the different ways technicians are compensated and how it can lead to resentment and difficulties in hiring new technicians. Ethical Profit and Long-Term Benefits (00:07:31) Explanation of how Matt's shop rewards employees based on ethical profit and how hiring bonuses can benefit both the shop and existing employees in the long term. The Mismanagement of Compensation (00:09:59) Discussion about the mismanagement of compensation in the aftermarket automotive industry and the potential impact on employees. Concerns about Flat Rate Pay (00:13:33) Addressing concerns about transitioning to a flat rate pay system and the potential negative impact on technicians' income and job satisfaction. Recommended Books for Auto Repair (00:19:49) Discussion on the importance of reading books on auto repair Building a Network in the Automotive Industry (00:26:06) Advice on how to build a network of connections in the automotive industry, including attending trade shows and utilizing social media. The importance of networking (00:29:42) The value of building relationships and networking in the automotive industry.  
      Thanks to our Partner, NAPA Autotech napaautotech.com
      Email Matt: [email protected]
      Diagnosing the Aftermarket A - Z YouTube Channel HERE
      Aftermarket Radio Network: https://aftermarketradionetwork.com/
      Click to go to the Podcast on Remarkable Results Radio
    • By Changing The Industry
      We have FREE training on Saturday in North Carolina!
    • By carmcapriotto
      Is your business prepared for cyber-attacks? It's not a question of 'if' it's a question of 'when.' Our panel discusses the importance of network security and protecting businesses from cyber threats. They emphasize the need for multiple layers of protection, including two-factor authentication, and caution against phishing attacks. They also highlight the importance of training employees to recognize such threats and having a proactive approach to cybersecurity. Let's stay ahead of potential threats and make it more difficult for hackers to target our businesses. Chris Cloutier is co-owner of Golden Rule Auto Care in Dallas Texas and CEO of Autoflow. Chris’s previous episodes HERE Jay Mikulovich, founder and CEO of Revival Technology LLC. Stan Stokes, Founder & CEO of Iron Fist Marketing Consultants. Stan's previous episodes HERE Show Notes:
      The importance of two-factor authentication (00:02:07) Explains the significance of using two-factor authentication to add an extra layer of security to passwords. The vulnerability of software packages (00:03:48) Discusses how no software is perfect and can have vulnerabilities, emphasizing the need for multiple layers of security. The dangers of phishing attacks (00:08:06) Explains the concept of phishing and how hackers use email to trick users into clicking on malicious links or attachments. The challenges of being reactive to security breaches (00:10:04) The difficulties of being reactive to security breaches and emphasize the importance of being proactive in protecting business operations. The vulnerabilities of relying on technology (00:11:24) The vulnerabilities of relying heavily on technology and the need for shop owners to understand their level of vulnerability and seek expert advice. The importance of backups and cybersecurity measures (00:20:38) Discussion on the need for backup plans, having multiple backups, and the importance of cybersecurity measures to protect against potential data loss or breaches. Difference between IT support and network security (00:23:39) Explaining the distinction between IT support and network security, and the importance of understanding and vetting service providers to ensure proactive cybersecurity measures are in place. Updating Network Security (00:27:58) Discussion on the importance of regularly updating network firewalls, equipment, and passwords to prevent hacking and security breaches. The Risks of Delaying Updates (00:28:51) Exploration of the consequences of not updating desktops, including vulnerabilities, outdated patches, and potential hacking threats. Password Management and Security (00:30:41) Advice on using password managers, generating unique passwords, and the importance of having strong, lengthy passwords to enhance security. The importance of strong passwords and data encryption (00:37:03) Discussion on the significance of using strong passwords and encrypting data to protect against cyber threats. Securing networks and vulnerabilities (00:37:54) Exploration of the importance of securing networks, including the use of firewalls and regular security scans, to prevent hacking and data breaches. Understanding APIs and their role in data protection (00:39:34) Explanation of APIs (Application Programming Interfaces) as a means of limiting data access between systems and the importance of authentication in ensuring secure communication. Take baby steps to minimize risk (00:46:05) The importance of taking small steps to implement cybersecurity measures and reduce the risk for business owners. Be the harder target (00:47:11) Being proactive in implementing security measures, such as cameras and updates, to make your business a less vulnerable target for hackers. Thanks to our Partners Shop-Ware and Delphi Technologies Shop-Ware: More Time. More Profit. Shop-Ware Shop Management https://getshopware.com/ Delphi Technologies: Keeping current on the latest vehicle systems and how to repair them is a must for today’s technicians. http://DelphiAftermarket.com Connect with the Podcast -Follow on Facebook: https://www.facebook.com/RemarkableResultsRadioPodcast/ -Follow on LinkedIn: https://www.linkedin.com/in/carmcapriotto/ -Follow on Instagram: https://www.instagram.com/remarkableresultsradiopodcast/ -Follow on Twitter: https://twitter.com/RResultsBiz -Join our Insider List: https://remarkableresults.biz/insider -All books mentioned on our podcasts: https://remarkableresults.biz/books -Our Classroom page for personal or team learning: https://remarkableresults.biz/classroom -Buy Me a Coffee: https://www.buymeacoffee.com/carm -The Aftermarket Radio Network: https://aftermarketradionetwork.com -Special episode collections: https://remarkableresults.biz/collections      
      Click to go to the Podcast on Remarkable Results Radio
    • Incfile.com
    • By carmcapriotto
      Recorded Live at ASTE 2023 Scott Brown discusses the evolving technology of Advanced Driver Assistance Systems (ADAS). He dives into the challenges and benefits of calibrating ADAS systems in vehicles, the future of level five automation and importance of technicians staying updated on technology advancements.
        Scott Brown, Founder of Diagnostic Network. Scott's previous episodes HERE. Show Notes
      Advanced Driver Assistance Systems (ADAS) by Steve Zack, Kurt Shadbolt and Scott Brown  The evolution of ADAS technology (00:01:17) Scott Brown discusses his early exploration of ADAS technology and how it has become more focused over the years. Understanding computer vision in ADAS (00:02:12) Scott Brown explains how computer vision works in ADAS systems and the importance of training cars to recognize objects in their environment. Advancements in camera technology (00:04:25) Scott Brown discusses the advancements in camera technology, including the ability to remove radar sensors and rely solely on cameras for functions like cruise control and pedestrian detection. The Lane Assist Experience (00:08:03) Discussion about lane assist technology and the adjustment to driving without it. Tesla's Shift to Vision System (00:08:40) Explanation of Tesla's decision to no longer use radar sensors and instead rely on their vision system for ADAS. Static calibration challenges (00:16:38) Increasing use of cameras for dynamic calibration (00:17:32) Benefits of backup cameras (00:18:20) The importance of technology in automotive education (00:25:18) The need for updated curriculums in automotive schools and the role of technology in education. The potential career opportunities for students in automotive technology (00:27:29) The Tesla's Full Self Drive Experience (00:32:16)  
      Thanks to our Partner, NAPA Auto Care
      Learn more about NAPA Auto Care and the benefits of being part of the NAPA family by visiting https://www.napaonline.com/en/auto-care
      Connect with the Podcast:
      -Follow on Facebook: https://www.facebook.com/RemarkableResultsRadioPodcast/ -Follow on LinkedIn: https://www.linkedin.com/in/carmcapriotto/ -Follow on Instagram: https://www.instagram.com/remarkableresultsradiopodcast/ -Follow on Twitter: https://twitter.com/RResultsBiz
      -Join our Insider List: https://remarkableresults.biz/insider
      -All books mentioned on our podcasts: https://remarkableresults.biz/books
      -Our Classroom page for personal or team learning: https://remarkableresults.biz/classroom
      -Buy Me a Coffee: https://www.buymeacoffee.com/carm
      -The Aftermarket Radio Network: https://aftermarketradionetwork.com
      -Special episode collections: https://remarkableresults.biz/collections
      Click to go to the Podcast on Remarkable Results Radio

  • Our Sponsors

  • Create New...