Generator "F" Field Circuit
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Powertrain Control Module (PCM) monitors the duty cycle of the generator through the "F" circuit. The generator "F" terminal is connected internally to the voltage regulator and externally to the PCM. As generator load increases, PCM can adjust idle speed accordingly.