2004 Cadillac XLR Owner's Manual - Page 160

Tire Pressure Light This light should come on briefly as you start the engine. It will then come on only when a low tire pressure condition exists. Malfunction Indicator Lamp Check Engine Light Your vehicle is equipped with a computer which monitors operation of the fuel, ignition and emission control systems. See Tire Pressure Monitor System on page 5-58 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. 3-50