Know Your Car Inside And Out: How To Hack It

Editors' Note: We've reviewed several cheap OBD II scanners under $100 to help you choose the best device for your needs.

There’s a secret feature in your car that your mechanic has done his best to keep a secret. Every car sold in the U.S. since 1996 features a built-in engine control computer that can be accessed with the right tools. This is called On Board Diagnostics-II (OBD-II), and it’s usually used as a way for mechanics to diagnose problems. But there’s no reason that you can’t use it as a way to look inside your engine and figure out what’s broken, what isn’t, and help and keep it running at peak performance. In other words, you can learn to hack into your car’s computer.

Some early car computers used a cryptic series of dashboard light blinks to tell you when something is wrong. Today, there are engine scanners and other products that can open a window into your car.

Until a few years ago, these OBD scanners cost thousands of dollars and were only sold to auto repair shops and mechanics. Now, there are some scanners that are small enough to put in your pocket. They’re just as sophisticated and have the ability to monitor actual engine parameters, like speed, temperature and voltage, but also track other vital areas, including the brakes, steering, ventilation and other items.

If you look around, these engine scanners seem to be everywhere. You can get one of them on Amazon, Sears or your nearest car parts store. You aren’t expected to be a professional mechanic to buy one anymore.

The key is that every time the car’s computer sees something that’s not quite right it stores a fault code and often turns on the dreaded Check Engine light. An OBD-II scanner can dig deep into the computer’s memory and extract these codes so that you can determine what’s going on under the hood. You can also make your car’s Check Engine light turn off, if you want.

There are literally thousands of fault codes. For example, if your car is idling roughly the OBD-II scanner can tell you whether it may be due toa vacuum leak (code P0171), a problem with the catalytic converter (code P0420) or something else entirely. None of these codes can be retrieved without such a scanner.

Great for diagnosing problems and second guessing car mechanics, the OBD-II scanner is today’s equivalent of traditional must-have auto repair tools, like a timing light, tachometer and Dwell meter. Every driver should have one because they’re inexpensive,  easy to use and can show what’s wrong with a car without ever going to a repair shop.

I believe that every car owner should take personal responsibility for the health of his car, rather than leaving it solely up to a so-called “professional”. Having an OBD-II scanner handy is a great start.

The hardest part about operating the scanner is figuring out where it plugs in to your car. Every car made since 1996 has an OBD-II plug located within 3-feet of the driver. It’s usually somewhere under the dashboard, behind a trim panel or between the front seats; some Hondas have a port hidden by the ashtray. Best bet: your car’s manual lists the location.

Along with jumper cables, a small tool kit and a tire pressure gauge, I keep a scanner in the back of my car. Sometimes it isn’t there when I need it: that’s because I often lend it to friends so they can diagnose their own car troubles.

In the pages that follow, I’ll take a look at three OBD-II devices that range from consumer friendly to professional by using them with my 2006 Mercedes E350 wagon. I’ll also show you ten issues  that an OBD-II scanner can help clear up. Here’s how to make the most of this technology.

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  • the OBD-II spec is an Open Standard. The port is openly accessible. Calling this "hacking" is just like crossing a crosswalk when it's green and calling it jaywalking. The port is there so anyone can hook up to it and do diagnostics.

    Now, if you were to get on the single-wire CAN network and reverse engineer some manufacturer-specific commands to control the locks/brakes etc, that would be considered hacking.
  • I happen to be an automotive technician and I have to say that some of these are great, but when it comes down to it I'll take a real piece of diagnostic equipment any day. Like the ETHOS EESC312W from snap on. Sure the actron is good but can it give you live data feeds from any sensor in your vehicle? or run your engine/transmission through a diagnostic test? Not only that but even best scanner on the market can not diagnose a mechanical problem, that's still left to the experience of the tech servicing the vehicle. Oh and by the way here's a link to what a real diagnostic tool looks like:
  • ram1009
    YAWN!! This story is at least 10 years late.
  • TomD_1
    "as well as whether you want it to report Metric or English units"

    English units? Don't you mean imperial units?
  • TwoDigital
    Kinds of bummed you left out the BEST scanning tool (plugs into a PC where you can use any of a dozen nice OBDII programs for tracking, etc...) scantool dot net.
  • truerock
    OK - I don't get it. Why wouldn't you connect your notebook conputer or iPhone to your car? Why do you have to buy a scanner?
  • truerock
    Well it took 3 minutes of research, but I guess you would use this cable to connect your car to your notebook computer:
    and you would use one or all of these free software applications:
    Opendiag, Freediag and/or pyOBD
    I don't understand why anyone would buy a scanner. Obviously the guy who wrote this useless article doesn't have a clue.
  • truerock
    OMG... I found it. I can hook my car up to my iPhone via OBDII...
    So far, I haven't found a cheap bluetooth interface... still looking
  • The problem with using this well known technology is demonstrated in the article. A catalytic converter causing rough engine idle? Unless the cat has spontaneously welded your exhaust shut on a car with wastegates, it is physically impossible for the cat to affect idle. So go ahead, "second guess your mechanic" based on an ODBII scan as this article suggests. See where that get you (maybe a blown transmission at 1am in the middle of nowhere).

    I use a BT scanner with USB output. Diagnostic and real time logging. Best of both worlds.

    Hacking a car, by the way, is done via the ECU, not the ODBII. ODBII is read only.
  • JohnnyLucky
    Interesting article. Never thought of trying to access my automobile's onboard computer.
  • Regulas
    I think it is an evasion of privacy and should be disclosed at time of purchase allowing the buyer to opt out. More nanny state big brother crap.
  • Indeed old news..
    for the nerds who want to hack their Volkswagen/Audi/Seat/Skoda there is a tool called VAG-com which allows you to change a lot more then just the service interval indicator ;-))
    In the netherlands there is one man who has a dedicated website for VAG-com and extensive lists of codes:
  • I'm an auto mechanic, for 44 years, and I'm all for people knowing more about their vehicles. :)

    With that said, there are a few problems with knowing a LITTLE about your vehicle.

    Fact is: auto repair is more complicated than brain surgery.

    OBD II programs have been available since 1996, one for the Palm handheld comes to mind, I believe it cost $89.00. including the cable.

    As another mechanic above (a little testily) pointed out, just getting the code doesn't give you the answer.
    Even when you know what the code is for.

    A stored code points in the direction the problem appears to be.
    and it could be wrong.

    I use a $7600.00 scanner, the Modis, and it's just a cheap, slow computer that may not be as powerful as an iphone, but, it contains megabytes of data, of tech tips, diagnostic procedures, some of which it can run for you right there on the spot.

    This is needed since this code needs to be interpreted a lot more, for example: a code for vacuum leak can be either: an actual vacuum leak of unknown source (many possibilities, none of which the code or computer can tell you where); an EGR problem (leaking EGR valve, which is rare); a leaking intake valve, or more.
    Tracking down the cause of the code often takes special equipment, lots of experience, expertise, and patience.

    Reading live data is useful if you know what they all mean. Often there are more than 60 parameters that the computer displays for you.

    Arming yourself with some of this when you do talk to your mechanic can help the problem be found.

    Not everyone can be a mechanic. a good one. :) It takes special skills, so, don't throw out your mechanic and try to do it yourself.
  • Does this scanner work on all cars?
  • " Well it took 3 minutes of research, but I guess you would use this cable to connect your car to your notebook computer: [...] onnectors/
    and you would use one or all of these free software applications:
    Opendiag, Freediag and/or pyOBD
    I don't understand why anyone would buy a scanner. Obviously the guy who wrote this useless article doesn't have a clue. "

    With more than 3 minutes research, the "gocha:"[mDepth]=2&tx_commerce_pi1[path]=38,37

    " Please note: The OBDII to serial cables are straight through and have no interface in them. Plugging them directly into a computer serial port will likely damage it. "
  • frankliverpoolfrank
    HI dos any one know were the scanner point on a hyundai coupe se 2000cc year 2001 thanks frank