The Mystery of automotive diagnostic equipment

It is no secret that dealers have the most state of the art diagnostic equipment in the industry. Everything from our $1100 battery testers, to our $12,000 VW scan tool.  In fact, the amount of dollars that are spent on special tools and equipment is truly unbelievable. With all that money wrapped up in scan tools, many folks think that they are magic boxes that fixes cars.

The high dollar equipment is just another tool. They are VITAL to repairing most cars, but they don’t fix cars. Would you believe me if I told you a wrench fixed a car?, NO, the wrench was needed to fix the car, it was the mechanic that fixed the car.

I can’t tell you how many times I have heard

“You can just hook it up to the computer and KNOW whats wrong with my car!”

Well, the truth is YES and NO. When I hook a car up to the scan tool, I read the information that is stored in the car’s computer. That information gives me the system that has failed. It does not say “replace this part”.

Take an Airbag light for example. When I use the scan tool to check faults, it will tell me the area that has a problem. If the fault is for the drivers airbag(the one in the steering wheel) that does not mean the airbag is bad. It just means that the system is faulty. The actual problem could be:

  • It could actually be the airbag in the steering wheel
  • the Airbag Module might be faulty
  • It could be the wires from the module to the airbag in the steering wheel
  • the “clock spring” might be faulty(see the bottom of the post for a description of this part)
  • the battery voltage might be causing a false error

Now, the scan tool will not say which one of these things have failed. That is where a mechanic comes in. The testing of components is where the problem is found. That is where the knowledge of the car, and the specific system is vital. It would be almost impossible to fix one of the failures listed above, if I didn’t know how it worked. I will say advanced diagnostic techniques for another post.

I think the issue comes mostly from service departments doing a poor job of helping cusotmers understand the process. Has your mechanic or service advisor ever taken the time to explain how this works? I would be willing to bet that very few have done that. I have heard it explained like this

“The diagnostic fee is $100. We will hook it to the computer and then tell you what is wrong with your car.”

That statement doesn’t really seem like your getting $100 in value does it? It just feels like a customer is paying $100 for a few minutes of work. If all things go right, hooking a car to the scan tool takes just a couple of minutes. –side note, that rarely happens, scan tools can get stupid sometimes– 🙂 Where the value comes from is

  • What the mechanic knows
  • the diagnostic equipment
  • the information available about repairing the car
  • special tools that it takes to fix the car.
What do you guys think? Does your mechanic/ advisor do a good just explaining things, and helping you understand what they are ACTUALLY doing? Do you even care, as long as the car is fixed?
**From above, A “Clock Spring” is what electrically connects your steering wheel to the rest of the car. It allows you to have a horn, and buttons on the steering wheel, and still use them with the wheel turned. The newer ones are a ribbon cable wrapper in a plastic housing. It has enough cable to allow the wheel turn fully in both directions. With the fault I talked about, this part is the most common failure.**

6 replies
  1. Kevin
    Kevin says:

    Special tools are expensive. The minimum required tool list for a new vw dealer is big. The cost is approx $275,000 in special tools just to open! That doesn’t include the $100,000 in alignment rack, brake lathe, tire mounter and balancer. So I would think you need about half a million just to start. But those tools are needed for PROPER diagnostic procedures to be completed. Huge cost be well worth it for doing good business.

  2. Jeremy Bechtold
    Jeremy Bechtold says:

    on top of that equipment and knowledgeable personnel, I know in other franchises you must also have a minimum amount of stock on-hand at all times. that half a million just went right out the window! it might have actually been my old tech from the dealer I bought my car from that told me about it, but I believe it was in the neighborhood of $2M+ (just in parts inventory) as you basically have to have certain parts on hand for the last 2-3 generations of all models, just in case someone comes in for a fix. they were a very small dealer around here, actually posted pictures of every person they sold to on a board for a running tally of 2+ years, and fit them on a couple corkboards. the showroom had room for maybe 3 cars if positioned well, and another 20 max out in the lot (shared by other vehicles in for repair too). my details could be off slightly, but I do recall the inventory being the main issue for smaller places.

    so many harley dealers have gone under in recent years even with great sales, as they independent mechanics are taking business away at a lower rate and the harley shops aren’t carrying the inventory and getting caught and losing franchises. they just cannot afford to leave parts on the shelves for years and years, but harley wants them to. I don’t know if they can become a dealer without being a repair site as well, but that would seem to be the only way to start a new one nowadays. maybe they could become a semi-wholesaler/supplier to those indie mechanics for parts, but I doubt they’d be able to stay afloat that way either. the profit would still probably fall below the cost to sit it on a shelf.

    • Humble Mechanic
      Humble Mechanic says:

      The amount of “big brother” is kinda scary. Our parts department can do what they want, but VW give incentives to keep parts on the shelf.

      You right though, its hard to sell jobs with no parts in stock.

      Part of the issues with motor cycles is, I think there are more DIY then with cars. Since a motor cycle is a hobby, lots of folks do their own..

  3. Jeremy
    Jeremy says:

    Because I know what a diagnosis I know its more than a scan but I have heard the service counter people say exactly what you said. It seems like a joke and turns people off to opting for it.

    If that was the case for $100 you can buy a scan tool and get the code for yourself. I have looked up codes before.. It gives a list of things that can be wrong, like you mentioned.

    Anyway, people have to be more informed about what exactly the diagnosis process is.


Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.