2009 Chevrolet Suburban Owner's Manual - Page 227

Charging System Light This light comes on briefly when the ignition key is turned to START, but the engine is not running, as a check to show it is working. Voltmeter Gage When the engine is not running, but the ignition is on, this gage shows the battery's state of charge in DC volts. If it does not, have the vehicle serviced by your dealer/retailer. The light should go out once the engine starts. If it stays on, or comes on while driving, there could be a problem with the charging system. A charging system message in the Driver Information Center (DIC) can also appear. See DIC Warnings and Messages on page 3-64 for more information. This light could indicate that there are problems with a generator drive belt, or that there is an electrical problem. Have it checked right away. If the vehicle must be driven a short distance with the light on, turn off accessories, such as the radio and air conditioner. When the engine is running, the gage shows the condition of the charging system. The charging system regulates voltage based on the state of the battery for improved fuel economy and battery life. The gage may transition from a higher to lower or a lower to higher reading, this is normal. Readings between the low and high warning zones indicate the normal operating range. The gage may also read low during the fuel economy mode, this is normal. 3-39