New Holland DCU 19676 – DCU: Ambient Temperature: SAE J1939 Check for CAN receive signal

The control module is not receiving a valid ambient air temperature reading over the SAE J1939 CAN bus network. The signal is either completely missing, out of its expected voltage/temperature range, or corrupted, which triggers a serial communication link error (P0600).

• New Holland T7 Series (T7.220, T7.235, T7.250, T7.260, T7.270)
• New Holland T8 Series

1. 1

   Check for related fault codes (such as P0071 or P0600) to determine if the issue is in the CAN bus wiring or the sensor itself.

2. 2

   Inspect the Ambient Air Temperature Sensor and connector for moisture, corrosion, or backed-out pins.

3. 3

   Test the CAN Bus Network by verifying the continuity and voltage of the CAN High and CAN Low wires between the Engine Control Unit (ECU) and the Dosing Control Unit (DCU).

4. 4

   Use a diagnostic scan tool to view the live ambient air temperature reading in the ECU to isolate if the fault lies in the CAN communication or the sensor/direct wiring.

1. 1

   Connect Diagnostic Tool

   Plug in your OEM diagnostic scanner and pull all active and stored codes from both the ECU and DCU.

2. 2

   Visual Inspection

   Trace the wiring harness from the Ambient Air Temperature Sensor back to the ECU, and the CAN bus harness from the ECU to the DCU. Look for chafed wires, rodent damage, or melted insulation.

3. 3

   Clean Connections

   Disconnect the Ambient Air Temperature Sensor and the DCU harness connectors. Apply electrical contact cleaner and ensure no pins are bent. Reconnect securely.

4. 4

   Perform Wiring Continuity Test

   Using a multimeter, test the resistance of the CAN bus lines (SAE J1939). Repair any open circuits or shorts to ground/power.

5. 5

   Replace the Sensor

   If the wiring is intact, the CAN bus is communicating properly, and the ECU is registering an out-of-range signal (often accompanied by code P0071), replace the Ambient Air Temperature Sensor.

6. 6

   Clear Codes and Test

   Clear the fault codes from the DCU and ECU. Cycle the key, start the engine, and monitor the DCU live data to ensure the ambient temperature signal is now reading 'in range' and the P0600/19676 codes do not return.