The light is not a component of the basic aircraft or covered in the basic P2+ RFM/FMS. My guess is it’s probably a component of an STC (Metro SPIFR kit perhaps?). Or is it installed on an aircraft with CDS panel? As shown above, the CPDS FAN failure warning is displayed on the PFD which refers to a failure of an avionics rack fan (see the RFM SUPPLEMENT FOR SINGLE/DUAL PILOT IFR OPERATION KIT).