1996 GMC Sonoma Owner's Manual - Page 103

Voltmeter When your engine is not running, but the ignition is on (in the RUN position), this gage shows your battery's state of charge i n DC volts. You can only drive for ashort time with the reading i n either warning zone. If you must drive, turn off all unnecessary accessories. Readings in either warning zone indicate a possible problem in the electrical system. Have the vehicle serviced as soon as possible. 9 19 VOLTS Brake System Warning Light Your vehicle's hydraulic brake system is divided into two parts. If one part isn't working, the other part can still work and stop you. For good braking. though, you need both parts working well. If the warning light comes on, there could be a brake problem. Have your brake system inspected right away. When the engine is running, the gage shows the condition of the charging system.Readings between the low and high warning zones indicate the normal operating range. Readings in the low warning zone may occur when a large number of electrical accessories are operatingin the vehicle and the engine is left at an idle for an extended period. This condition is normal since the charging system is not able to provide f ~ r l power at l engine idle. As engine speeds areincreased, this condition should correct itself as higher engine speeds allow the charging system to create maximum power. BRAKE This light should come on briefly when you turn the ignition key to RUN. If it doesn't ccme on then, have it fixed so it will be ready to warn YOLI if there's a problem. 2-55