Case IH 19677 – DCU: Ambient Temperature: SAE J1939 Check for CAN receive signal : (Signal Range Check: Signal not in range / Erroneous Signal / Signal not available) _timeout _P0071 Ambient Air Temperature Sensor Range/Performance.

The control module is not receiving a valid ambient air temperature signal over the SAE J1939 CAN bus network. The signal is either timing out (not available), out of its expected operating range, or sending erroneous data.

• Tier 4a
• Tier 4b
• Magnum Series (235 - 340, Series 4)
• Steiger Series (350 - 600 HP)

1. 1

   Visually inspect the Ambient Air Temperature Sensor, connector, and wiring harness for physical damage, corrosion, or loose pins.

2. 2

   Connect a diagnostic scan tool and monitor the live ambient air temperature value to check for extreme default values (e.g., maximum temperature or absolute zero) indicating a hard fault.

3. 3

   Disconnect the sensor and use a multimeter to check the signal circuit for a short to ground or an open circuit.

4. 4

   Verify that the CAN bus communication lines between the Engine Controller and the DCU are intact, as the DCU relies on the engine module to broadcast this temperature data.

1. 1

   Power Down

   Turn off the machine and disconnect the battery ground to prevent electrical spikes during repair.

2. 2

   Locate the Sensor

   Find the ambient air temperature sensor near the air cleaner assembly.

3. 3

   Inspect and Clean

   Disconnect the sensor harness. Spray the connector pins with electrical contact cleaner to remove any dirt or moisture.

4. 4

   Test the Sensor

   Test the sensor's resistance with a multimeter. If the internal resistance is completely open or shorted, the sensor has failed and must be replaced.

5. 5

   Repair Wiring

   If the sensor tests good, trace the wiring harness back to the ECM/DCU. Repair any chafed wires or broken connections that could be interrupting the J1939 CAN signal.

6. 6

   Replace and Reassemble

   Install the new sensor (if faulty) and securely click the harness connector into place.

7. 7

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the active and stored 19677 / P0071 fault codes from the DCU.

8. 8

   Test Run

   Start the engine and verify that the ambient temperature reads correctly on the dash/scan tool and that the fault code does not return.