I Circuit 1816 (YE/LB)
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
This is the GEN COM circuit. The PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator via the GEN COM circuit.