Snap-On Scanner Scenario

Feb 15, 2003

RAY: We have in our shop a device which is called the scan tool, and ours is made by Snap On, and it's a wonderful thing, and I suppose most shops have such a device. Anyway, you take the scan tool and you connect it to usually a plug under the dashboard or under the hood and it extracts valuable information from the car's computer. And once we get that information, then we can accurately misdiagnose a whole range of problems.

TOM: Right.

RAY: Recently we got a new piece of software for our scan tool, and one of the guys plugged it in, and he starts scrolling through the data and looking for readings that are out of the normal range. For example, it might say that the engine operating temperature is minus 40 degrees and that might give you an idea that something is wrong with the coolant temp sensor. Or you forgot to pay the heating bill at the garage or something like that. Anyway, as this fellow is scrolling down looking for all this information it gives you, I was looking over his shoulder, and he comes to a thing that says, "tire pressure low, right front." And he says, "Huh?"

So I walk around to the right front and, sure enough, it looks pretty low -- it's almost flat -- and I say, "Geez, it's right." And he says, "How does this thing know? There's no air pressure monitor in this car." And that's the question. How did the scanner know?


RAY: Now we all know that when a tire loses its air it gets smaller. And if your car had a device that could measure how much the car was tilting, it could in fact tell you if it was tilting towards the right front, it could tell you in fact that it was the right front tire that was low. But unfortunately --

TOM: It doesn't have such a device.

RAY: But when a tire loses air pressure and its diameter gets smaller, when the car is going down the road, in order for that tire to keep up with all the others and not get left behind, it has to turn faster. And your car does have something that is constantly monitoring the speed of all the wheels and comparing them to one another.

TOM: Yes.

RAY: And what most modern cars have is --


RAY: Antilock brakes. And there's a sensor at every wheel that's reading how fast each of the wheels is going on average. So, if it notes that the right front wheel is going a heck of a lot faster than the other wheels, it can either assume that you're making a lot of left hand turns or driving around a circle...or that your right front tire is going flat.

TOM: Wow.

RAY: Who's our winner.

TOM: The winner is Jean Sager from Wessington, South Dakota.

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