TM 9-2320-364-20-2 2-1334 20.  REVERSE LIGHT DOES NOT OPERATE (CONT). Work lights operate indicating   10 to 14 vdc to circuit breaker   CB3. Circuit breakers CB3 and CB4   OK. Engine starts indicating 10 to 14   vdc to wire 1871. Reverse light backup lamp OK. Wire 1149 OK. Wire 1435 OK. Wire 1891 OK. Wire 1871 OK. Wire 214 OK. Wire 1149 OK. Reverse relay R10 faulty. ATEC ECU faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Voltage test. STE/ICE-R #89. If 10 to 14 vdc is measured, ATEC ECU is faulty. If 10 to 14 vdc are not measured, relay R10 is faulty. YES NO Replace reverse relay R10 (Para 7-95). Verify repair, go to Step 9 of this Fault. 8. Are 10 to 14 vdc measured on wire 1149 at reverse relay R10, terminal 87, when wire 214 at harness connector MC50, terminal D is jumpered to ground? 7. Go to Step 8 of this Fault. YES NO Work lights operate indicating   10 to 14 vdc to circuit breaker   CB3. Circuit breakers CB3 andCB4   OK. Engine starts indicating 10 to 14   vdc to wire 1871. Reverse light backup lamp OK. Wire 1435 OK. Wire 1891 OK. Wire 1871 OK. Wire 214 OK. Wire 1149 faulty. Reverse relay R10 faulty. ATEC ECU faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Voltage test. STE/ICE-R #89. If 10 to 14 vdc is measured, wire 1149 is faulty. WARNING Are 10 to 14 vdc measured on wire 1149 at reverse relay R10, terminal 87? Replace ATEC ECU (Para 7-71).   Verify repair, go to Step 9 of this Fault. Repair wire 1149 (see schematic Fig 2-33) or notify DS Maintenance.  Verify repair, go to Step 9 of this Fault. WARNING Read WARNING on Page 2-1335 Read WARNING on Page 2-1335