2008 Hummer H2 Owner's Manual - Page 188
2008 Hummer H2 Manual
Page 188 highlights
Readings in the low warning zone may occur when a large number of electrical accessories are operating in 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 full power at engine idle. As engine speeds are increased, this condition should correct itself as higher engine speeds allow the charging system to create full power. If there is a problem with the battery charging system, this light will come on or the SERVICE BATTERY CHARGING SYSTEM DIC message will display. See DIC Warnings and Messages on page 3-56 and Charging System Light on page 3-37 for more information. Your vehicle's hydraulic brake system is divided into two parts. If one part is not 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 and a chime sounds there could be a brake problem. Have your brake system inspected right away. This light may also come on due to low brake fluid. See Brakes on page 5-36 for more information. Brake System Warning Light With the ignition on, the brake system warning light will come on when you set the parking brake. If you try to drive with the parking brake engaged, a chime will sound when the vehicle speed is greater than 5 mph (8 km/h). United States Canada This light should come on briefly when you turn the ignition key to RUN. If it does not come on then, have it fixed so it will be ready to warn you if there is a problem. 3-38