1999 Cadillac DeVille Owner's Manual - Page 133

yellowblue Engine Coolant Temperature Gage This gage shows the engine coolant temperature. If the gage pointer moves into the red 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. Analog Cluster That reading means the same thing as the warning light -- the engine coolant has overheated. See "Engine Overheating" in the Index. 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 and a chime will sound 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. 2-73