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Posted

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

Posted

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.

Posted

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

[/quote

 

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

Posted

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

[/quote

 

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

  • 4 weeks later...
Posted

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.

 

Sorry...

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         0 comments
      The Technician Shortage Is Our Fault, And It's Time We Own It
      Nearly every day, I hear shop owners complain: "There's a technician shortage. We can't find qualified people. There's no one out there." If that's true, then who's to blame?
      The industry? The schools? The government? I don't know how you feel, but who promised us an endless supply of qualified technicians?
      Another common complaint is that young people do not want to work in the trades. Well, if that were true, then why are other trades such as HVAC, electrical, and plumbing growing? What are they doing that the automotive industry is not? 
      Here's the reality we need to face: We do have a problem, but we shouldn't look for someone or any entity to rescue us. Not the government. Not the trade schools. Not the recruiting companies. No one owes us a workforce. If we want great people in our industry, it's up to us. At some point, we need to own up to the truth: Building a pipeline of qualified technicians is our responsibility.
      In this blog article, I will break down the key reasons we are in this situation today and what we, as an industry, can do to solve the technician shortage. Are you ready to look in the mirror?
      Have We Pushed Technicians Away?
      Let's take a look at flat-rate pay. True flat rate, which pays a technician only for the hours they produce, is a controversial pay plan that emphasizes high production levels and creates a competitive work environment that, if not properly controlled, can lead to increased mistakes and a decline in morale and team spirit. Additionally, the stress and physical demands placed on technicians as they age are not favorable to long-term employee retention. What do we do with technicians as they grow older into their fifties and begin to slow down? 
      I have heard all the arguments and pros and cons of flat-rate pay, and I am not going to judge any pay plan. Let the facts speak for themselves. True flat rate has changed in most areas around the country and has evolved into a pay plan that gives technicians some pay guarantee.
      Many shop owners have learned that team morale, along with the opportunity to earn income, is important to technicians and to the company's long-term success. But let me ask you: how many technicians have left or been pushed out over the years because of the old flat-rate pay system?
      Another issue is the workplace environment. I remember being grateful to be hired as a young technician at a local repair shop. While very thankful, the work environment was not ideal. The shop owner kept the bay doors open year-round (I am from New York) unless it rained or snowed. He felt that if the bay doors were closed, customers might think we were closed for business. We had no heat and no hot water. Many of the jobs were done outside, year-round,  in all types of weather. The starting pay was minimum wage, with no benefits, sick days, or vacation pay. 
      Now, again, I need to point out that I was truly grateful for the opportunity this shop owner gave me. I learned a lot working there, and the experience was pivotal in my career. But looking back, I wonder how many people were discouraged by these working conditions?
      While the physical demands of the repair workplace are daunting, perhaps even more critical is the culture. Too many of my generation shop owners preached the mindset of "my way or the highway." We were the business owners, after all. We started our companies, took all the risks, and provided jobs. Why shouldn't we be the ones to set the ground rules our way?   
      Many of us found over the years that the "my way or the highway" mentality was a sure way to isolate employees and make them more likely to look over the fence for greener grass. In other words, it led many technicians to seek employment elsewhere, where they felt they could be appreciated and recognized for their hard work. The issue, however, was that there wasn't much green grass around. Disappointment after disappointment, bouncing from repair to repair shop, eventually led to despair. So, I ask you: were workplace conditions a contributing factor in today's technician shortage?
      Another factor that we are all well aware of is the complexity of the modern automobile. When I started, the work was mostly physical, and you were required to master essentially three vehicle models: General Motors, Ford, and Chrysler. Let's fast-forward to today. The evolution of automotive technology, along with the extensive training and tools required, has outpaced the typical technician's pay compensation, with no clear career path. Again, leading to frustration and insecurity about the future.
      Here is the bottom line: people don't leave their job; they leave their experience. We must do a better job. 
      The News Isn't all Bad; Your Next Steps to Fix the Technician Shortage
      To fix the technician shortage, it will take a combined effort from everyone in the automotive industry, particularly automotive shop owners. Shop owners are in the perfect position to make the greatest impact, not only on their businesses but also on the future automotive workforce.
      First, shop owners must become better leaders and understand that their ultimate success is directly dependent on the people they assemble around them. Any shop owner who mistakenly believes they can build an empire solely on their abilities is destined for serious disappointment. Business owners who think like this will eventually plateau. Without the collective contributions from a team of qualified people, your business will stall; it will not continue to grow.
      Create a workplace that attracts top talent: a clean, professional, well-equipped facility designed to support productivity, teamwork, and a career, not just a job. Build a great reputation in your community by getting involved locally. Become the auto repair shop that people take notice of as "the" place to work.
      Next, shop owners must become more financially knowledgeable. Knowing your numbers and what you need to achieve for a strong bottom-line profit is essential to paying technicians the money they need and deserve. Profit will also allow you to compete with other trade industries by providing a benefits package that has real take-home value and security.
      When it comes to culture, this is where the rubber hits the road. People crave recognition, praise, and a sense of purpose. Despite what you hear, people are not just money-motivated. Once people feel secure in their financial situation, retaining and motivating technicians can only be achieved by connecting with them on an emotional level. You cannot show enough appreciation. Give out praise for a job well done as if your business depended on it, because it does.
      As technicians age, we need to have a place for them. Expecting a 58-year-old to perform like a 35-year-old is unrealistic. We need to be more focused on career pathing. Provide training, skill development, and coaching to develop leaders and mentors within our older workforce. While their bodies may have slowed, the knowledge they have gained is priceless. 
      Our future is dependent on young people entering our industry. We need to give more young people opportunities. Every shop owner across the country should consider hiring an apprentice, then build an apprentice training plan and career path for them. If every shop did this, we could solve the technician shortage within five years. Get involved with the trade schools and high schools in your area. Look into the NAPA Apprenticeship Program. Don't sit on your hands with this one. Do it today.
      Lastly, don't get left behind. Commit to ongoing training for all your employees. Keep up to date with tools and equipment tailored to your business model. Don't try to be all things to all people and all vehicles. Identify your core profile customer and the vehicles they drive, and become an expert on those vehicles and the services you offer.
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