STEP/SEQUENCE RESULT WHAT TO DO NEXT TM 9-2320-363-20-1 Section 4 TROUBLESHOOTING CHARTS E.  FLASH CODE: 27 J1587 CODE: P1723 - AIR TEMPERATURE CIRCUIT FAILED HIGH (HIGH VOLTAGE) NOTE - This chart is only to be used if: 1) All basic mechanical checks and physical inspections have been performed with no problem found, and 2)    Diagnosis of DDEC-III was started at step Start-1, pg 3-345.41 and you have now been referred here. 27-1 Sensor Check Turn ignition off. Code 172/4 (or any Go to 27-2. Disconnect ATS and install jumper. other codes except wire between the ATS connector Code 172/3). sockets A and B. Turn ignition on. Anything except - Go to 27-4. Read active codes Code 172/4. 27-2 Check for Short to +5 Volt Line Turn ignition off. Less than or Signal line (ckt#132) is shorted Remove jumper wire. equal to 10,000 ohms. to the engine +5 Volt line (ckt Disconnect engine harness #416), and/or (ckt#132) connector at the ECM. signal is shorted to (ckt#452) Read resistance between sensor return and/or ground, sockets N2 and W1 on engine Repair short.  Then go to 27-30. harness connector. Greater than Go to 27-3. 10,000 ohms or open. 27-3 Check ATS Connectors Inspect terminals at the ATS Terminals and Replace ATS.  Then go to connectors (both the sensor and connectors are okay. 27-30. harness side) for damage; bent, corroded, and unseated pins or Problem found. Repair terminals/connectors sockets. Then go to 27-30. 27-4 Open line Check Turn ignition off. Less than or Go to 27-5. Disconnect the engine harness equal to 5 ohms connector at the ECM. Read resistance between sockets Greater than Signal line (ckt#132) or return N2 and Y2 on the engine harness 5 ohms or open. line (ckt#452) is open.  Repair connector. open.  Then go to 24-30. Change 3  3-345.259