Diagnostic Aids
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The voltmeter may fluctuate between 12 and 14 volts. This is normal operation. For further information, refer to Charging System Description and Operation or refer to Voltmeter gauge under the Instrument Panel section in the owners manual.