New Holland INST 12111 – INST: Communications Lost with Automatic Temperature Controller

The tractor's Controller Area Network (CAN bus) is no longer receiving data messages from the Automatic Temperature Controller (ATC) module, which manages the cab's HVAC (Heating, Ventilation, and Air Conditioning) system.

• T8000 series (T8030, T8040)
• T9000 series (T9020, T9030, T9040)
• TG series (TG215, TG245, TG305)
• T7 series
• T9 series
• CR9000 series (CR9040, CR9060, CR9070, CR9080, CR9090)
• CX8000 series

1. 1

   Check for accompanying 'Communications Lost' codes (e.g., INST 12071, INST 12091, INST 12101) to rule out a global CAN bus failure

2. 2

   Check the cab fuse panel for blown fuses or tripped relays dedicated to the HVAC/ATC system

3. 3

   Bench test the CAN bus terminators by supplying 12 volts to terminal 1 to ensure network resistance is intact

4. 4

   Inspect the wiring harness connecting the ATC to the main cab harness for chafing, pinched wires, or loose connector pins

1. 1

   Isolate the Power

   Turn off the machine and disconnect the battery to prevent electrical shorts during testing.

2. 2

   Access the ATC Module

   Remove the interior cab trim panels to access the rear of the Automatic Temperature Controller (typically located on the right-hand console or integrated into the headliner/HVAC panel depending on the model).

3. 3

   Inspect the Connector

   Disconnect the ATC wire harness. Inspect the pins on both the module and the harness for corrosion, pushed-back pins, or moisture intrusion.

4. 4

   Test the Circuit

   Using a multimeter, verify that the harness is delivering 12V power and a solid ground to the ATC module.

5. 5

   Test the CAN Lines

   Measure the resistance across the CAN High and CAN Low pins at the connector. A healthy CAN bus with both terminators intact should read approximately 60 ohms.

6. 6

   Replace Components

   If the wiring harness is damaged or failing continuity tests, replace the ATC wire harness. If power, ground, and CAN bus resistance are all within specification, the ATC module has suffered an internal hardware failure and must be replaced.

7. 7

   Clear Codes

   Reconnect the battery, turn the ignition on, and use a diagnostic tool (such as the CNH Electronic Service Tool or Jaltest) to clear the INST 12111 fault code and verify that communication with the ATC has been restored.