Circuit 586 (RD/PK)
WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. However, it is still accessible from the selected car via links, so may be relevant.
This is the generator communication (GEN COM) circuit. The PCM determines the optimal voltage set point for the charging system and communicates this information to the voltage regulator on the GEN COM circuit.