2009 GMC Envoy Owner's Manual - Page 170

Tire Pressure Light For vehicles with a tire pressure light, this light comes on briefly when the engine is started and provides information about tire pressures and the Tire Pressure Monitoring System. When the Light Flashes First and Then is On Steady This indicates that there could be a problem with the Tire Pressure Monitor System. The light flashes for about a minute and stays on steady for the remainder of the ignition cycle. This sequence repeats with every ignition cycle. See Tire Pressure Monitor System on page 5-63 for more information. Malfunction Indicator Lamp When the Light is On Steady This indicates that one or more of the tires is significantly underinflated. A tire pressure message in the Driver Information Center (DIC), can accompany the light. See DIC Warnings and Messages on page 3-51 for more information. Stop and check the tires as soon as it is safe to do so. If a tire is underinflated, inflate to the proper pressure. See Tires on page 5-53 for more information. Check Engine Light A computer system called OBD II (On-Board Diagnostics-Second Generation) monitors operation of the fuel, ignition, and emission control systems. It ensures that emissions are at acceptable levels for the life of the vehicle, helping to produce a cleaner environment. 3-38