See Figure 1
There are many Saturn test procedures that require the connection of a scan tool. In addition to that, 1991-95 models have the added ability to connect a jumper wire to terminals A and B of the ALDL (the main diagnostic tool connector). The ALDL (1991-95 models) or DLC (1996-98 models) is used during vehicle assembly to test the engine before it leaves the assembly plant, and after the leaving the factory to communicate with the PCM. The ALDL is located under the left side of the dashboard, near the hood release handle. Terminal A is an internal ground and is the top right terminal in the connector. Terminal B, directly adjacent and to the left of Terminal A, is the main diagnostic terminal. When these terminals are jumpered together, and the ignition switch turned ON , the SERVICE ENGINE SOON light will flash Code 12. This indicates that the internal diagnostic system is operating and that specific output device signals are being generated.