Ignition Circuit Sense
WARNING: This page is about a different car, the 2003 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
This circuit is used to tie the ignition switch to the PCM. The ignition circuit sense input tells the PCM the ignition switch has energized the ignition circuit. Battery voltage is also supplied to the PCM through the ignition switch when the ignition is in the RUN or START position. This is referred to as the ignition sense circuit and is used to "wake up" the PCM. Voltage on the ignition input can be as low as 6 volts and the PCM will still function. Voltage is supplied to this circuit to power the PCM's 8-volt regulator and to allow the PCM to perform fuel, ignition and emissions control functions.