Audio Unit
WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The audio unit can be powered up when the key is in RUN, ACC, or START. The audio unit provides audio signals to the speakers, thus producing sound. The audio unit directs the audio signals to the speakers through separate positive and negative circuits for each of the 4 audio channels: LH front, RH front, LH rear, and RH rear. The audio unit provides internal circuit protection for shorts to ground and shorts to battery.