Circuit Description
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
The DTC P1600 Control Module Long Term Memory Reset diagnostic detects a loss of battery voltage to the control module's keep alive memory circuit. Battery voltage is supplied to Powertrain Control Module (PCM) even when the ignition switch is OFF. Battery positive voltage is used for PCM keep alive memory and air-fuel ratio adaptive control memory. If DTC P1600 is set, PCM will not store any other DTCs.