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Help with learning more about OBD2 and CANbus in vehicles

  1. Jul 1, 2017 #1
    I am wanting some advice on where to go with learning more about the electronic systems used in modern cars. I have a basic understanding of how the systems work, (ECU, BCM, etc) but I'm wanting references for books, videos, websites on it, as I've watched most of the Youtube vids, and found a few websites that focus only on basics and code definitions. The 2 books I've found seem to only focus on code definitions and diagnosis, whereas I'm wanting more of the technical stuff, signals, sensor types, capabilities, etc.

    I find it very neat that most new cars are actually running a whole network with all kinds of sensors, switches, valves, etc. and it's all tied in over a 2 wire network. My car, for instance has 5 different computer modules that tie in together over the CAN bus. The hybrids like Prius and Volt must have 10 times that (would love the wiring diagrams/schematics for one of them!) I just want to learn for my own knowledge, and to better understand modern cars.

    Thanks for any advice!
  2. jcsd
  3. Jul 3, 2017 #2
    Hi Lineman,
    Unfortunately there is not much published data about the specifics of the various car manufacturer data buses, or the capabilities of all the various cars. The buses and instrumentation typically go way beyond the OBDII stuff. OBDII is only the 'required' interface and codes. The rest of it is information that they typically play very close to the chest, and only release some of it to tool manufacturers with a need to know. Even then, they only divulge the information needed to meet their own goals or what might be mandated by after-market repair laws.

    In a way, you can see their point. Some of the information can turn a modern car into a locked brick, with no way to open the doors without breaking glass. I know, I used to work for a major diagnostic tool manufacturer, and even with "all" of the information, we bricked a couple of cars before they released some more of the details. But we had to replace the main control computer in order to open the car doors. Now, with wireless entry systems, you don't even need to plug into the diagnostic port to do the same thing.

    Also, emission control software is very sensitive information to both the manufacturer and the EPA - look at what happened to VW. The software in the diesels only reverted to low emission mode when the diagnostic tool was plugged into the car (ie while being tested), then went back to 'dirty' mode.

    Unfortunately, about the only way to learn much about the details is to get involved in the industry somehow.
  4. Jul 3, 2017 #3


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    IIRC, the emission control change was triggered by engine speed and no activity of the steering wheel. Obvious but somewhat clever, I thought.
  5. Jul 4, 2017 #4

    jim hardy

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    Car enthusiast forums would be a good place to start. "Gearheads" are playing with their cars, hacking the computers and having a jolly good time.

    Try a search on Mustang Forums, and forums for whatever you drive.

    There are interfaces on the market that'll let you plug your PC to the car's diagnostic port and monitor Canbus traffic,
    Here's an introduction to the electrical interface.

    and here's just one of many interface gizmos

    Wish i could help you but my car interests lie in the other direction.
    '68 Ford 'bumpside' pickup - "No EGR, No Computer, No Problem"

    Have fun, become the neighborhood Canbus guru.

    old jim
  6. Jul 4, 2017 #5


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    A few sources for OBD (On Board Diagnostics) readers:

    Plugs in to the Serial port of a (laptop) computer for a comprehensive display. Paid for itself the first time that the Check Engine light came on (bad O2 sensor). Has pretty good documentation.

    Haven't used their stuff but they at least used to have an OBD reader that plugged in to a USB port on your computer.
  7. Jul 4, 2017 #6
    Thanks for the replies! I was able to find a PDF for a Toyota Prius, and wow, about everything is connected to the networks. In the case of Toyota, there appear to be 3 networks all tied in. The CAN bus, something called BEAN (body electrical area network, iirc) and a net for audio visual stuff, such as stereo, hands free phone, navi, etc. They all communicate over a special gateway module that seems to act as translator.

    I remember hearing about the VW emissions deal, that was ingenious, although more evil genius, but still...
    I have a Bosch scan tool, it shows me why the check engine light is on, but also shows stuff like RPM, coolant temp, freeze frame, etc. I just know there is much more info available at the DLC port than what my tool can access. I worked in a shop for a few years doing tires and oil changes, we had a Snap On Modis, that thing could do about everything. I don't think it did immobilizer/keys, but it did everything else!

    As for the hackers, there are some neat (if not scary) vids of what can be done to a car while it's being driven! Thankfully, it seems security experts agree it's fairly hard for an average person to carry out these attacks, and likely not common. Plus, the auto makers are working to fix these vulnerabilities as they arise.

    Bill, you mentioned wireless entry and not having to plug into the port. I thought the wireless side only covered accessing the car, either via a fob, or in the case of Onstar like systems, calling them and getting them to unlock the car after verifying who you are. I didn't think it covered diagnostics wirelessly too, has this changed?
  8. Jul 15, 2017 #7
    I also found a book called The Car Hackers Handbook, which the author has put online for anyone to read. That has a ton of info on what I was wanting, and I'd suggest it to anyone who wants to learn about car electronics or car security.
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