TM 1-1510-225-10 3B-171 Table 3B-102.  Fault Codes and Descriptions CODE DESCRIPTION AND COMMENT 00 No fault found. 02 RAM test failed.  Unit unusable (µP problem). 03 No serial data to unit.  Unit unusable (CTL problem). 04 No serial frequency word.  Unit unusable (CTL problem). 05 Invalid NAV frequency.  (CTL may be tuned to DME channel). 06 Microprocessor fault.  Unit unusable. 10 Microprocessor fault.  Unit unusable. 11 Analog to digital fault.  Unit unusable. 12 Analog to digital failed accuracy test.  Unit unusable. 13 +13 Vdc power supply fault.  Unit unusable. 14 -13 Vdc power supply fault.  Unit unusable. 15 VOR sin  è/LOC digital to analog fault. LOR/LOC unusable. 16 VOR cos è/GS digital to analog fault. VOR/GS unusable. 17 VOR receiver synthesizer unlocked.  VOR receiver inoperative. 18 VOR AFC not locked.  VOR unusable (no rf signal). 19 Low 30-Hz reference signal.  VOR unusable. 20 Low 30Hz variable signal.  VOR unusable. 21 400-Hz power supply unusable.  VOR OBI and OBS unusable. 22 OBI sin out of tolerance.  VOR OBI and OBS unusable. 23 OBI cos out of tolerance.  VOR OBS unusable. 24 OBS return out of tolerance.  VOR OBS unusable. 25 LOC synthesizer unlocked.  LOC receiver inoperative. 26 LOC signal level low.  LOW unusable. 27 LOC deviation out of tolerance.  LOC deviation unreliable. 28 GS synthesizer unlocked.  GS receiver inoperative. 29 GS signal too low.  GS receiver inoperative. 30 GS deviation out of tolerance.  GS deviation unreliable. 32 Marker beacon fault.  Observe marker lamps for fault. 3B-22.  TACAN SYSTEM. The TACAN system has been removed from the C-12T3. 3B-23.  DISTANCE MEASURING EQUIPMENT (DME). a.   Description.     DME  readout  is  displayed  on the   EHSI   in   the   upper   left-hand   corner.      Distance readout  can  be  read  to  the  course  source  or  to  the bearing  source.    Course  sources  are  selected  by  the Course    Source    Selector    (FMS    or    VOR)    and    the CRS1/2 button (#1 or #2).  The bearing button selects the  navigation  source  to  be  displayed  on  the  EHSI bearing  pointer.    Bearing  selections  are:    Off,  FMS1, FMS2, VOR1, VOR2, ADF1, ADF2. (1)   Course Source Distance Readout.  When distance is available for the selected course source the distance  source  and  the  distance  in  nautical  miles  to the NAV source is displayed in the upper left corner of the  MFD.    If  the  source  course  is  FMS,  the  active waypoint  is  displayed  as  the  distance  source.    If  the course   source   is   VOR,   DME   is   displayed   as   the distance source.