2001 GMC Sierra 1500 Pickup Owner's Manual - Page 170

Voltmeter CAUTION: If the air bag readiness light ever comes on when you have turned off the air bag, it means that something may be wrong with the air bag system. The right front passenger's air bag could inflate even though the switch is off. If your vehicle is a regular cab pickup and this ever happens, don't let anyone whom the national government has identified as a member of a passenger air bag risk group sit in the right front passenger's position (for example, don't secure a rear-facing child restraint in your vehicle) until you have your vehicle serviced. If your vehicle is an extended cab pickup and this ever happens, don't let anyone whom the national government has identified as a member of a passenger air bag risk group sit in the right front passenger's position (for example, don't secure a rear-facing child restraint in the right front passenger's seat) until you have your vehicle serviced. United States Canada When your engine is not running, but the ignition is in RUN, this gage shows your battery's state of charge in DC volts. 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. 2-87