The year was 1980. GM came out with the Assembly Line Diagnostic Link otherwise known as the ALDL. It was used as a tool for diagnosing on-board computer functions prior to the vehicle being rolled off the assembly line. Shortly afterward, the entire industry jumped on board, using this connection as an access point to the brains of the vehicle for servicing it. This was the beginnings of the scan tool.
Modern scan tools are much more advanced than these early, rudimentary devices. They can diagnose a wide variety of troubles that would otherwise take a great deal of time to resolve. When using a modern scan tool, the first order of business is to inspect various vehicle components to rule out any mechanical problems that might trigger a false trouble code. The technician should check wiring, hoses, cables and more.
Diagnostic Trouble Codes (DTC’s) would be the most frequent reason for use. These codes are not necesarily a diagnosis of the specific problem, but the are an indicator of a problem within a specific system or area of the car. These codes provide a starting point, but they do not typically point to the specific problem. Chasing codes has been further expanded in more recent years as many states adapot OBD II checks instead of the more traditional testing through the tailpipe of the automobile.
When purchasing a scan tool, you’ll want to choose one that meets a wide range of uses. Make sure you can see what kinds of codes will be displayed. Some scanners only list generic OBDII codes, not providing the most precise detail that you need.
Some problems within certain vehicle systems cannot show up in the trouble codes. In these circumstances, it is up to the experienced technician to decipher the serial data, or Parameter Identification Date (PID). If a sytem falls outside of it’s normal specified values, you need to investiugate further.
Just as with any thing, a scan tool is a tool to assist you, but it is not a cure-all.