Computer Controlled Shutdown
WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 2007 Mercury Mountaineer, 2007 Mercury Monterey, 2007 Mercury Montego, 2007 Mercury Milan, and 2007 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.
The PCM controls the electronic engine control (EEC) power relay when the key is turned to the ON or START position, by grounding the PCM relay control (PCMRC) circuit. After the key is turned to the OFF, ACC or LOCK position, the PCM stays powered up until the correct engine shutdown occurs.
The ignition switch position run (ISP-R) and the injector power monitor (INJPWRM) circuits provide the key state input to the PCM. Based on the ISP-R and INJPWRM signals the PCM determines when to power down the EEC power relay.