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Know Your Car Inside And Out: How To Hack It

Diagnose Me

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.