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Car Talk: Basic scanner just fine for ‘shade tree mechanic’

Dear Car Talk: I’m a “shade tree mechanic” and recently bought an OBD-II/CAN scanner. I chose the cheapest unit I could find (about $25), and it seems that all it will do is read and/or clear any codes that are set. Since I have the factory service manual for my car, I can look up the codes to see what’s wrong or do a Web search if I need more information. What I’m wondering is: If I spent more on a fancier unit, what additional features would I get? Can my basic unit read all codes from all systems in my car? I don’t need the unit to tell me what the code means or how to fix it. Thanks! – Larry

A: If you don’t need to know how to fix the car, then what you bought is absolutely good enough.

Your unit should be able to read all of the codes and, just as important, clear the codes so you can turn off the “check engine” light.

If you bought a fancier unit, besides the leather seats and sunroof, you would get some features that we find helpful in the shop. First, it helps you with the diagnosis. If it reads a code on a Subaru for a bad evaporative emissions system, for instance, it might tell you to “check for a rusted filler neck, since that’s the most common cause of leaks in this system.”

That’s helpful, but you often can find that same kind of information on the Internet. Or you can do what my brother would have done: Put a match to the filler neck and see if it ignites.

As a shade tree mechanic, you have plenty of time to search the Web for answers. But since we’re fixing 20 cars a day, it’s helpful to give our guys immediate information like that. Plus, every time they do an Internet search at the shop, they end up spending all day at entertainment sites and not fixing cars.

The other nice thing that our scanners do is let us actuate certain components, which also helps in diagnosis. For example, if we’re diagnosing an overheating problem, we can push a button on our scan tool and tell the car’s computer to “energize the cooling fan.”

That’s a quick and easy way to find out if the fan, the wiring and the relay are all working. Otherwise, we would have to let the car run for 10 minutes until it got hot enough to turn on the cooling fan itself, and spend a bunch of time with a test light.

These more sophisticated scanners also can communicate wirelessly with the software in our garage’s computer, and pull up wiring diagrams and stuff like that.

But the units we use cost several thousand dollars. And those features are just not worth the money for a shade tree guy working on one car on the occasional weekend.

So what you have is perfect. You’ll read the code, and then you run back and forth into the house to look up stuff online. Just bring a rag to wipe the grease off the computer keyboard so your family doesn’t lock you out.

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