It doesn't quite work that way. A diagnostic computer is typically a handheld device that plugs into a service port on the car and allows the technician to view the same data that the computer accesses. The diagnosis does not pop up on the screen, however. The technician must read voltages, vacuum readings, and other data to determine which parts are operating correctly. Is a sensor not operating? Or is its electrical connection bad? If a system is failing, the computer will store a code that helps the technician find the root cause of the problem.

Technicians rely on computer diagnostics just as doctors analyze medical test results before performing surgery. Like doctors, they must have the training and experience to interpret the data delivered by sophisticated tests.

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