• Choose a category
• All
• Classic-Fiction

By Root 314 0

to standardize their diagnostics under a protocol called OBD-II (for onboard diagnostics), but as any mechanic will tell you, sometimes the system gives the wrong trouble code. Being off by one digit might give a diagnosis of “System fuel too lean on bank one” (P0171), that is, an air-fuel mixture that is too much air and not enough fuel on the first bank of cylinders, when in fact the problem is “System fuel too rich on bank two” (P0172). An experienced mechanic can tell too lean from too rich by looking at the spark plugs; they will look blanched white in the first case and sooty in the second. Representing states of the world in a merely formal way, as “information” of the sort that can be coded, allows them to be entered into a logical syllogism of the sort that computerized diagnostics can solve. But this is to treat states of the world in isolation from the context in which their meaning arises, so such representations are especially liable to nonsense. To rely entirely on computer diagnostics would put one in the situation of the schoolchild who learns to do square roots on a calculator without understanding the principle. If he commits a keying error while taking the square root of thirty-six and gets an answer of eighteen, it will not strike him that there is anything amiss. For the mechanic, the risk is that someone else committed a keying error.15

Computerized diagnostics don’t so much replace the mechanic’s judgment as add another layer to the work, one that requires a different sort of cognitive disposition. Tommy related the story of a late-model Kawasaki liter-class sport bike that came in. The customer reported that it was down on power, and there was an engine light flashing. Bob checked out the bike and could find nothing wrong, so he got ahold of the manufacturer’s service manual for the bike, which gave instructions for retrieving a trouble code from the onboard diagnostic system. After this step you look up the code in a list to find out what the problem is.

The trouble code specified only that the issue was in the intake system, and directed him to a test procedure that would further narrow down the problem. In following the test procedure in the Kawasaki book, Bob got to a point where he said, “This is bullshit,” and handed it off to Tommy. This is an important moment I would like to understand; we will return to it shortly.

Tommy worked through the procedure, which consisted of measuring impedances and voltages across various circuits and comparing them, as well as differences between pairs of them, to values listed in the book. He did this using a digital multimeter, which is the only way to get the precision you need. As anyone who has used such a meter knows, at the higher sensitivity settings used in much diagnostic work the reading tends to bounce around, and not in the way the old analog meters did, with the sweep of a pointer. With such a pointer the central value of, and variation in, the reading is represented spatially. With a digital multimeter what you sometimes get is a screen that won’t settle down; it flashes different readings, often so quickly that you can’t register them. Making matters worse, each of the ten digits is made up of little lines, just like in a digital watch (thus, an eight is a zero with an extra line across the middle, for example). As they flicker around, there is no inherent spatial mapping from what you see to the information represented. Sometimes it seems the screen’s response is slower than the meter’s time-wise integration of the underlying thermal noise that is generating the variation, so you get nonsense digits.16 For example, you might get a backward nine. Or is that a P? What does that mean? Positive? Polarity?

The net effect on me is often the same as it was on Bob: “This is bullshit.” The digital multimeter, together with the procedure in the book, present an image of precision and de terminacy that is often false. What the procedure in fact demands of you is a real effort of interpretation, one that is nowhere acknowledged in the service manual.