Vehicle Power (VPWR)
WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
When the key is turned to the ON or START position, battery positive voltage (B+) is applied to the coils of the EEC power relay and power sustain relay (PSR). Since the other end of the coils are wired to ground, this energizes the coils and closes the contacts of the EEC power relay and PSR. VPWR is now supplied to the PCM and the EEC system as VPWR. When the key is turned to the OFF position, the PCM keeps the PSR energized until the normal power-down sequence is completed. For additional information, refer to ENGINE CONTROL COMPONENTS , Power Sustain Relay.