GM Service Manual Online
For 1990-2009 cars only

Voltage is applied through the 20 A PWR/CIGAR fuse at all times to the cigar lighter through fuse output-battery circuit. The cigar lighter has a heating element. Pushing in the cigar lighter completes the circuit to ground through the ground circuit and heats the cigar lighter. When the element is sufficiently heated, the cigar lighter opens the circuit.