2010 GMC Savana 2500 Cargo Owner's Manual - Page 177

When the Light is On Steady This indicates that one or more of the tires are significantly underinflated. A tire pressure message in the Driver Information Center (DIC), can accompany the light. See Driver Information Center (DIC) on page 4-37 for more information. Stop and check the tires as soon as it is safe to do so. If underinflated, inflate to the proper pressure. See Inflation - Tire Pressure on page 6-63 for more information. Malfunction Indicator Lamp 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. This light should come on when the ignition is on, but the engine is not running, as a check to show it is working. If it does not, have the vehicle serviced by your dealer/retailer. If the check engine light comes on and stays on, while the engine is running, this indicates that there is an OBD II problem and service is required. When the Light Flashes First and Then is On Steady This indicates that there may 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 Operation on page 6-66 for more information. 4-31