TM 9-2320-360-20-1 2-13.  INTRODUCTION TO LOGIC TREE TROUBLESHOOTING (CONT) Table 2-5.  DDEC Troubleshooting KEY SYMPTOM A.  CHECK ENGINE Indicator comes on and stays on. SECONDARY SYMPTOMS PAGE A1 CHECK ENGINE indicator on and code 25 on DDR  ............................................................................. 2-94 A2 CHECK ENGINE indicator always on, no data link, codes not flashing.   ................................................ 2-98 A3 DDR display blank or random ............................................................................................................ 2-102 A4 DDR reads active code other than code 25, and does not read any historic codes. Flash SAE Codes: Codes: Code 11 P187 4 Vernier Control Signal Voltage Low........................................................... 2-106 Code 12 P187 3 Vernier Control Signal Voltage High.......................................................... 2-116 Code 13 P111 4 Coolant Level Sensor (CLS) Signal Voltage Low........................................ 2-122 Code 14 P175 3 Oil Temperature Sensor (OTS) Signal Voltage High ................................... 2-126 Code 15 P175 4 Oil Temperature Sensor (OTS) Signal Voltage Low.................................... 2-130 Code 16 P111 3 Two Piece Coolant Level Sensor (CLS) Signal Voltage High....................... 2-134 Code 21 P091 3 Throttle Position Sensor (TPS) Signal Voltage High ................................... 2-142 Code 22 P091 4 Throttle Position Sensor (TPS) Signal Voltage Low.................................... 2-148 Code 23 P174 3 Fuel Temperature Sensor (FTS) Signal Voltage High................................. 2-158 Code 24 P174 4 Fuel Temperature Sensor (FTS) Signal Voltage Low.................................. 2-162 Code 31 Fault on Auxiliary Output  .......................................................................... 2-166 Code 32 ECM Backup System Failure.................................................................... 2-172 Code 33 P102 3 Turbo Boost Sensor (TBS) Signal Voltage High ......................................... 2-174 Code 34 P102 4 Turbo Boost Sensor (TBS) Signal Voltage Low.......................................... 2-180 Code 35 P100 3 Oil Pressure Sensor (OPS) Signal Voltage High......................................... 2-188 Code 36 P100 4 Oil Pressure Sensor (OPS) Signal Voltage Low ......................................... 2-194 Code 41 S021 0 Timing Reference Sensor (TRS)............................................................... 2-204 Code 42 S021 1 Synchronous Reference Sensor (SRS)...................................................... 2-216 Code 43 P111 1 Low Coolant Level ................................................................................... 2-228 Code 44 P175 0 High Oil Temperature............................................................................... 2-234 Code 45 P100 0 Low Oil Pressure ..................................................................................... 2-236 Code 46 P168 1 Low Battery Voltage ................................................................................. 2-238 Code 51 Check Engine Light Comes On and Stays On............................................ 2-244 Code 52 S254 12 ECM - Analog to Digital Failure ................................................................. 2-246 Code 53 S253 12 EEPROM Failure Affecting Code Memory  ................................................. 2-248 Code 56 ECM - Analog to Digital Failure ................................................................. 2-250 Codes 61-68 Sxxx 0 Injector Response Times Too Long........................................................... 2-252 Codes 71-78 Sxxx 1 Injector Response Times Too Short  .......................................................... 2-264 Code 85 P190 0 Engine Overspeed .................................................................................2-265.1 A4A Check Vehicle Harness +5 Volt Supply...................................................... 2-266 A4B Check Engine Harness +5 Volt Supply ...................................................... 2-274 2-76  Change 3