Charging System Warning Indicator
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster receives the charge signal from the PCM over the communication network. When the generator (Escape, Mariner) or DC/DC converter (Escape Hybrid) output is insufficient to maintain the battery state of charge, the instrument cluster illuminates the charging system indicator.