The Society of Automotive Engineers assigned Diagnostic Trouble Codes, commonly known as DTCs, mainly as recommendations. Most car manufacturers follow DTCs, but not all of them. Your 1999 Buick has engine codes specific to the car. The Buick DTC "P1118," for instance, represents the engine code "Engine Coolant Temp Signal Out-Of Range High." Knowing how to retrieve the engine codes lets you know exactly where to start testing your car.
Turn off the engine.
Locate the 16-pin data link connector underneath the steering column. Remove the connector cover if it has one.
Plug in your OBD-II code scanner to the data link connector. The OBD-II system controls your engine and monitors the diagnostic control network of your car, as well as parts of the body accessory units and chassis. All cars built since January 1, 1996, which includes your 1999 Buick, have OBD-II and the scanners continue to evolve, becoming more sophisticated each year.
Turn on the ignition to your car. You do not need to start the engine to read the DTCs.
Follow the manufacturer's instructions for your OBD II code scanner to get the DTCs. DTCs will appear on your code scanner display, if they exist.
