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Any Open Source Solutions For DIY Auto Diagnostics? 270

slaxx writes "As an avid tinkerer, I really want to collect as much data about my car as possible. Using On-Board Diagnostics (OBDII) sounded great to me, but the pricetags of systems like AutoTap Scanner are a bit much for my college budget to handle. Are there any free, open source solutions available? What do Slashdotters do to tinker and record the inner workings of their own vehicles?"
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Any Open Source Solutions For DIY Auto Diagnostics?

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  • To Expensive? (Score:2, Insightful)

    by Anonymous Coward

    If $199 is to expensive for the hardware and software onyour Budget what do you expect to be able to fix on the car for cheaper?

    • Re: (Score:3, Informative)

      by rob13572468 ( 788682 )

      Thats true: you can always get something cheap like this: []

      Which is like $99 and it will work fine but you lose out on getting stuff like CAN monitors, API's and programming examples with the better adapters... Your best bet is to go with something like this: []

      which is a full featured adapter that you can actually do development and project work with.

    • Re: (Score:3, Informative)

      If $199 is to expensive for the hardware and software onyour Budget what do you expect to be able to fix on the car for cheaper?

      Something that would be $199 cheaper having not had to pay for software and hardware.

    • Re: Too Expensive? (Score:4, Insightful)

      by frisket ( 149522 ) <peter @ s i> on Sunday May 16, 2010 @11:24AM (#32227634) Homepage
      I don't want to tinker, but if I fix something simple like an air filter, I want to be able to reset the console warning lights.

      Currently you need a specially-adapted laptop, a highly proprietary cable, and some very expensive software. Garages can afford this: individuals can't.

      • Re: (Score:3, Informative)

        by Svartalf ( 2997 )

        It depends on what you're resetting. If it's the MIL you're wanting to reset, that may be accomplished with a simple OBDII reader that places like Wal-Mart and most reputable auto parts places will sell you for about $60-90. You're going to find that it'll cost more to read CAN or the other protocols than it's worth if all you're looking for is reset capability.

        However, if you're into tinkering and are looking for understanding the OBDII or a base platform for getting it into your laptop, you'll spend $20

      • Re: (Score:3, Informative)

        by blincoln ( 592401 )

        I don't want to tinker, but if I fix something simple like an air filter, I want to be able to reset the console warning lights.

        If you just want to be able to read diagnostic codes and reset the warning light(s), at most you need a standalone OBDII device, not a laptop, special hardware and software. Harbor Freight has them for US$50 right now [], and I got one on sale there for about $30.

        The only reason I know of to go the laptop route is to get detailed engine data like an emissions-testing station or perfor

      • Re: (Score:3, Informative)

        If that is all you want AutoZone/AdvanceAuto will usually reset the lights and read the codes for free. They'll try and sell you the part to fix it, but they don't force you to buy it.

        I use VCDS [] on my VW because when I'm diagnosing a problem on my car, I don't want to simultaneously diagnosing my tools.

        It takes time and money to reverse stuff. There have been a few open source projects, but all stalled or weren't kept up to date. I see there's a new VW project on SF.

        And as far as development goes, don't ask

    • Re:To Expensive? (Score:5, Informative)

      by xs650 ( 741277 ) on Sunday May 16, 2010 @01:32PM (#32228444)
      "If $199 is to expensive for the hardware and software on your Budget what do you expect to be able to fix on the car for cheaper?"

      More that you might expect.

      Last three items that my PC based and inexpensive OBD-II diagnostics helped me diagnose on my cars were:

      1. Poor connection at O2 sensor, cleaned connector cost $0.00

      2. Bad water temp sensor, $15.00

      3. Loose hose on air intake. Found because MAF readings were out of range. $0.00

      I could have eventually fixed any of those without the OBD-II reader but it would have taken a lot more time to find the problem, or I could have bent over in front of some dealer service adviser and grabbed my ankles like a typical consumer and paid some big dollars.

      The OBD-II codes didn't tell me exactly what to fix/replace on any of those but it greatly reduced trouble shooting time.

      Also Google the codes the OBD-II spits out, odds are your car isn't the first with the problem. On item 2, Google told me that the water temp sensor had a high failure rate so I started there. A simple ohmeter check told me my sensor was dead.

      Info for nervous Nellies, simple OBD-II readers are read only, so don't get your knickers in a knot.
      • Re:To Expensive? (Score:5, Insightful)

        by Anachragnome ( 1008495 ) on Sunday May 16, 2010 @03:19PM (#32229294)

        "The OBD-II codes didn't tell me exactly what to fix/replace on any of those but it greatly reduced trouble shooting time."

        THIS. Yes, IN CAPS.

        Scanners and shop scopes are GREAT for locating problems, but they do NOT replace a well-trained mechanic. Above poster makes it sound simple, but he already had an understanding of automotive tech. For example, using out-of-spec MAF readings to diagnosis an intake leak is one thing, but those readings could also be caused by intake valve issues, worn piston rings or a plethora of other things including a bad MAF sensor.

        My point is that an understanding of the underlying systems is still required.

        Don't expect a scanner, or even the information provided by one, to "fix" your car. They simply point you in the right direction (sometimes) and also allow you to verify the repair worked as planned.

        A side point. A cheap scanner will never have a "snap-shot" function, while a decent one will. This is CRUCIAL in diagnosing intermittent failures. Otherwise, you will be sitting there trying to make the problem occur while you have the scanner hooked up, often missing the 20ms failure. Blink and you miss it. A good scanner will store "frames" of info to go back and examine.


  • bad idea (Score:2, Insightful)

    by Anonymous Coward

    I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.

    • Re:bad idea (Score:5, Informative)

      by nhtshot ( 198470 ) on Sunday May 16, 2010 @08:56AM (#32226882) Homepage []

      Get rid of the proprietary crap and tinkering can be just as much fun!

    • Re: (Score:3, Informative)

      by rwa2 ( 4391 ) *

      Who cares about the proprietary chipsets when there are ISO standards for gathering data from them? []

      There have been mandatory standards for over 10 years, if only to make emissions testing faster by allowing the VEIP to plug directly into the OBD-II / CAN port under your dash to get emissions readings right from your engine instead of having to hook up that chemical analyzer to your exhaust.

      • Yes, but OBD standard only specifies some common elements, every car manufacturer now has extended proprietary commands along with standard one but you need to buy expensive licenses to obtain specs and use them in yur tool. This is main reason why those simple OBD plugs are so expensive, hardware costs about $20.
        • by horatio ( 127595 )
          I work for a company that makes equipment to control aspects of and interface with existing vehicle systems, primarily emergency and commercial vehicles (firetrucks, ambulances, buses and the like). Even we have a hell of a time getting straight answers out of the manufacturers (Ford, etc) when we ask about proprietary network messages (ie seatbelt latched) - regardless of the fact that we're not competing with them to build vehicles.
      • by cynyr ( 703126 )
        hehe, i'm not sure either of my cars have an ODBII interface, a '94 saturn SL2, and '95 ford escort ex or lx which ever is the cheeper trim option.
    • Re: (Score:2, Insightful)

      by kiwieater ( 1799016 )

      Tinkering? The whole point of these scanners is to read information and help diagnose problems.

      He could do more harm to the "safety of others around" him by advancing the ignition curve, leaning out the mixture, and melting the piston crowns. Or - if he had less sense and went about it the wrong way - working on the assumption that more fuel = more pwer, thereby flooding the followers on the road with a stream of unburnt fuel.

    • He is talking about diagnostics, which shouldn't really be too dangerous in itself.
      Also, the chips might be propriety but the connection and the codes/protocol are standard.
      I guess he could screw up and read the code for brake-system-will-not-maintain-pressure as gas-cap-loose but in general I don't see how it could pose much of a threat to anyone.
    • I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.

      You've apparently got no understanding of what the OBD II interface lets you do.

      OBD II lets you read trouble codes and operational data (sensor values, fuel integrator, ignition timing, etc.), and lets you clear trouble codes.

      That's it. There's no danger at all. You can't alter anything other than clearing trouble codes.

      To the original poster, google for "ELM327" to find the hardware, and "ELM327 software" to find software, including many free apps that will use the ELM interface to talk to OBD II.

      I use a

      • by rrossman2 ( 844318 ) on Sunday May 16, 2010 @10:00AM (#32227174)
        WRONG. OBD-II can do a lot more than that. For example in GM's, pin 2 at the ODB-II connetor will allow you to read tach signals, turn on heated accessories, control the OEM alarm and door locks, bypass the Passkey 3, etc. That's where remote start/alarm interface modules for GM cars tap into the CANbus (j1850).

        The radio in GM's (2001+) also don't have an accessory wire, it uses data as well which appears to also be tagged into the same CANbus. You must use a module to keep the factory chimes and create an accessory for you (you could just run your own ACC line but you lose all the features controlled via the radio over the data link). I've heard numerous times from other installers where an idatalink rem start/alarm module wouldn't program to a GM correctly with the aftermarket radio/adaptor installed. Unplug the adaptor, plug the factory radio in, and everything programs fine. So on some makes/models there's a lot more running over that CAN interface than you have any idea about.
        • by jimicus ( 737525 )

          In unrelated news, a GM spokesman denies putting wholly unrelated features into the radio in order to encourage owners to upgrade by purchasing an OEM radio at approximately four to eight times the price of an equivalent aftermarket model.

      • ah forgot a link:

        idatalink list for 2010 Chevy Colbolt []

        This is just using the features they provide for a remote start install. But you can really muck things up using just pin 2 of the OBD-II port on GMs. In fact you can make the whole car either A> not run properly or B> cause the car to shut down fairly easily via the CANbus.
      • by horatio ( 127595 )
        That isn't entirely true. Many of the obdii systems are now linked with the vehicle CAN bus, meaning you can screw things up royally if you do it wrong. We were experimenting on a Ford Escape a couple of months ago, trying to determine what commands were sent for things like seatbelt or ABS event. We built an OBDII connector, but a minor short in our harness caused the entire instrument cluster, radio, etc to wig out. There was no permanent damage, but it demonstrated that simply plugging something into
    • I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.

      And OBD2 port is just a serial port. Actually, there are several different types of OBD2 hardware interfaces, but they all follow the same basic protocol [] from a software perspective. I understand we have Congress to thank for that much. The proprietary parts are the PIDs that manufacturers add for specific product lines but the basics are pretty consistent. Besides ... querying your vehicle's ECU in the precise manner in which it was designed to be queried hardly constitutes tinkering with a proprietary chi

    • How is this different from fixing your own breaks, steering or even tires? Even A blowout can be dangerous. And doing all of that is quite legal in every country i have lived.
  • by Anonymous Coward

    It's the underlying protocol of OBD II.

    • by Mashiki ( 184564 )

      Was going to mention this, but glad to see someone beat me to it. It's really not that hard to make your own scanner, in fact when I was in high school(over 15yrs ago), we built our own OBDI/II computer diagnostic scanner for our shop, hooked upto an Amiga1000. And you're talking about a bunch of guys(and one girl); who knew nothing about computer programing at the time. Or the basic understanding of the system. But we could follow directions, and knew how to wire breadboards. If there's someone here o

  • OBD (Score:2, Informative)

    Just do a quick search on hackaday, there's been several projects in the past which may be helpful to you.
  • by mystik ( 38627 ) on Sunday May 16, 2010 @08:17AM (#32226692) Homepage Journal

    When I have the time, i've been meaning to try something like this: []

    Into my Car so I can get additional performance gagues + graphs. I have the Arduino board, and can solder things here and there, I've just never gotten around to it ....

    • If you want to use it as a digital dash, don't. ATMegas can't reliably run at fast enough serial rates to pump out the data fast enough for a real dash display. With all the stuff you want to display you'll end up at 5-10 updates a second, which just sucks.

      If you just want to futz around and see whats there before digging in, its fine.

      Realistically though, you can get a ODB-II to RS232 protocol converter for $40 or so, which is probably about $10 more than you paid for your arduino and it'll work far bett

  • scantool (Score:5, Informative)

    by cptdondo ( 59460 ) on Sunday May 16, 2010 @08:38AM (#32226800) Journal

    Look at [] . I use a Scangauge II. I went through this same thing; in the end I decided that buying a scangauge gave me 90% of what I wanted, out of the box, without having a computer clutter up the driving area, and without spending weeks hacking up something that might work but then again might not.

  • obdii hw, sw (Score:3, Informative)

    by Thng ( 457255 ) on Sunday May 16, 2010 @08:42AM (#32226818)
    First, get the hardware interface: [] with some OK software, $60 [] $29 shipped from hong kong. Hardware isn't free unless you really do want to build your own. ELM327 is a common OBDII interface chip, and they're probably nearly identical internally Then go to, software downloads, and find the source. Hack away. Or, go to sourceforge and look at some of the linux based obdii software.
  • Slashdotters telecommute, so the only vehicle is the comp..

  • RomRaider [] is available for Subaru vehicles.
  • Right to Repair (Score:2, Informative)

    by Tokolosh ( 1256448 )

    Support your right to repair: []

  • First off, there's a few different variants of CAN. For the basic OBD-II set they are mostly the same.

    Here is a link to a forum thread with links to basic/starter info: []

    I know GM uses j1850 for their OBD-II/CAN setup. Some of the things that can be read off of pin 2 at the OBD-II connector include Tach signal, bypass the chip-in-key, control door locks (mostly on 2001 and up though some older ones apply as well), con
  • Go to Autozone (Score:3, Informative)

    by Sycraft-fu ( 314770 ) on Sunday May 16, 2010 @10:05AM (#32227202)

    They'll read your ODB unit at no charge. Reason is, of course, they hope that you will then elect to buy the part(s) you need from them to fix it. Just go in and ask, they'll bring out a portable unit that reads the diag codes. They'll take that back to a computer, upload the results, and give you a printout.

  • If you are looking to read codes/reset codes then autozone will do it for free.. or sell you a scanner for 79.

    but as has been said... if 99-199 is too much, then don't even think about trying to enter into this very expensive hobby.

    even ultra low budget and open source solutions are more than $99, even if you build the ecu yourself like with older megasquirt systems []
  • Most local auto part supply stores will happily loan you an OBDII diagnostic tool for free. I've done this many times to read fault codes out of my car. It may not be as sexy as rolling your own, but it meets your price requirement.


  • by JustOK ( 667959 )

    When will it be the Year of Linux on the blacktop?

  • I went with Carman [] for Nokia's Maemo platform and a generic Bluetooth scantool. The advantage of this setup is that the Nokia webpad serves as an in-car media player, GPS unit and car computer, providing me with real-time diagnostics, positioning and entertainment.

    For fault diagnostics, I gave up in the end. At least for my car, (an Audi S8) it seems there are error codes that are manufacturer specific. Without a translation table, the error codes aren't particularly useful and I couldn't find any software

  • Autozone will read and clear trouble codes for free. So if you just have a one time need, do that.

  • I only have one car and I can't afford to have it not working so I don't tinker with it. I certainly am interested but I cannot afford the downtime. I can do it vicariously by going to the shop and watching the mechanic.

    I have a computer that I need for work and I don't tinker with that either. But on that front at least I can afford to have another that I can mess with.

    Thermodynamics fascinates me too but not enough to start taking apart my refrigerator.

    Good lord if my mechanic were ever like the ones t

  • TuxMobil provides a short (actually there a four entries) survey of Linux solutions for cars and automobiles []. BTW: there are a lot more free and open source solutions for bicycles [] yet.
  • Someone posted about a tool called "Scantool" [] on Ubuntuforums [] a few years ago.
  • True DIY (Score:3, Informative)

    by dissy ( 172727 ) on Sunday May 16, 2010 @12:40PM (#32228078) []

    Check out the ELM327 chip on that page.

    $33, rs-232 control of the chip and the chip speaks to ODBII: ISO 15765-4 CAN, SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2, ISO 14230-4 and SAE J1939 protocols

    You set the chip up with what to monitor and/or control (Similar in style to sending AT commands to a modem) and then it does the work of giving you the data stream.

    Build your own standalone test gear, with or without a PC interface.

    Googling for "ODB-II Connectors" was how I found the jack ends with pins to solder to. They varied in price a bit so where I purchased from 2 years ago no doubt isn't the cheapest now.

    Have fun

  • [] purchase of article required
  • by justinlee37 ( 993373 ) on Sunday May 16, 2010 @04:07PM (#32229558)
    But can someone explain what this article is about using a car analogy?

One can't proceed from the informal to the formal by formal means.