2002 Buick LeSabre Owner's Manual - Page 139

Engine Coolant Temperature Gage This gage shows the engine coolant temperature. If the pointer moves into the shaded area, the engine is too hot. Malfunction Indicator Lamp (Service Engine Soon Light) Your vehicle is equipped with a computer which monitors operation of the fuel, ignition and emission control systems. A temperature indicator light will turn on and a chime will sound. If you have been operating your vehicle under normal driving conditions, and the temperature indicator light comes on, you should pull off the road, stop your vehicle and turn off the engine as soon as possible. This system is called OBD II (On-Board Diagnostics-Second Generation) and is intended to assure that emissions are at acceptable levels for the life of the vehicle, helping to produce a cleaner environment. The SERVICE ENGINE SOON light comes on to indicate that there is a problem and service is required. Malfunctions often will be indicated by the system before any problem is apparent. This may prevent more serious damage to your vehicle. This system is also designed to assist your service technician in correctly diagnosing any malfunction. 2-76