2006 Cadillac STS-V Owner's Manual - Page 211

Engine Coolant Temperature Gage This gage shows the engine coolant temperature. Malfunction Indicator Lamp Check Engine Light Your vehicle is equipped with a computer which monitors operation of the fuel, ignition, and emission control systems. It can be used to see when your engine has warmed up and to make sure your cooling system is operating properly. If the gage pointer moves into the shaded area, the engine coolant is too hot and the engine coolant temperature warning light will come on. See Engine Overheating on page 5-31 for more information. 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 Check Engine 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. Notice: If you keep driving your vehicle with this light on, after awhile, your emission controls may not work as well, your fuel economy may not be as good, and your engine may not run as smoothly. This could lead to costly repairs that may not be covered by your warranty. 3-67