New Holland DCU 19679 – DCU: SAE J1939 Check for CAN receive signal

The control unit is monitoring the CAN bus network but the ambient temperature or barometric pressure signal it is receiving is either out of the acceptable physical range, completely missing, or erratic.

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• New Holland wheel loaders

1. 1

   Connect the CNH Electronic Service Tool (EST) and monitor live data for Ambient Air Temperature and Barometric Pressure to see if readings are stuck at a default extreme (e.g., -40°C) or fluctuating wildly.

2. 2

   Check for other active CAN-related codes (such as 19678) to rule out a broader CAN bus wiring issue causing multiple modules to drop offline.

3. 3

   Locate the ambient air temperature sensor (often integrated into the Humidity Sensor or Intake Air Temperature Sensor) and inspect the pigtail connector for backed-out pins, moisture, or corrosion.

4. 4

   Verify that the sensor is receiving its standard 5V reference voltage and has a solid ground to the Engine ECU.

1. 1

   Power Down

   Turn off the machine, remove the key, and turn off the master battery disconnect switch to prevent electrical spikes.

2. 2

   Locate the Sensor

   Find the ambient air temperature sensor. Depending on the model, it is typically mounted on the air cleaner housing, the intake piping, or just behind the front grille.

3. 3

   Disconnect the Harness

   Carefully depress the locking tab on the electrical connector and pull it free from the sensor.

4. 4

   Remove the Sensor

   Unbolt or unclip the faulty sensor from its mounting location. (If it is a threaded intake sensor, use the appropriate deep socket or wrench to back it out).

5. 5

   Install the New Sensor

   Fit the replacement sensor into the housing. If it is a threaded sensor, tighten it to the OEM torque specification (do not overtighten, as the plastic intake housings can crack).

6. 6

   Reconnect

   Plug the electrical harness back in, ensuring the weather-seal seats properly and the locking tab clicks.

7. 7

   Clear Codes

   Turn the battery disconnect back on. Connect your diagnostic tool, clear the DCU 19679 and P0071 fault codes, and cycle the ignition.

8. 8

   Test

   Start the engine and verify that the ambient temperature displays correctly on the cab monitor or diagnostic tool and that the fault code does not return.