New Holland INST 12021 – Instrumentation Controller (INST): Communications Lost with Auxiliary Controller

The data bus (CAN bus) communication link between the tractor's main instrumentation panel and the auxiliary/remote hydraulic controller has been interrupted or lost.

• TG210
• TG230
• TG255
• TG285
• T6000
• T7000
• T8000
• TM Series
• Magnum
• MX

1. 1

   Verify Module Functionality: Ensure that both the instrument controller and the remote hydraulic controller are receiving power and ground.

2. 2

   Check Connector C055: Check connector C055 at the remote hydraulic controller to ensure it is fully plugged in, seated correctly, and free of corrosion.

3. 3

   Inspect the Data Bus: Check the CAN bus lines between the instrumentation and the auxiliary controller for continuity, shorts to ground, or shorts to power.

4. 4

   Check for Accompanying Codes: Look for other INST codes (like INST 12043 - Communications Lost with Data Bus 1 and ALL other controllers). If multiple 'Communication Lost' codes are present, the issue is likely a main data bus failure rather than an isolated auxiliary controller issue.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Controllers

   Locate the Auxiliary/Remote Hydraulic Controller (often located near the rear hydraulic valves or under the right-hand cab console depending on the model) and the main Instrumentation cluster.

3. 3

   Inspect Wiring & Connectors

   Trace the wiring harness between the two modules. Disconnect connector C055 at the remote hydraulic controller.

4. 4

   Clean and Reconnect

   Inspect the pins for pushed-out terminals, moisture, or green corrosion. Clean the contacts with electrical contact cleaner, apply dielectric grease, and firmly reconnect the plug.

5. 5

   Test CAN Bus Resistance

   With the battery disconnected, measure the resistance across the CAN High and CAN Low pins at the diagnostic connector. A healthy CAN bus should read approximately 60 ohms. If it reads 120 ohms, a terminating resistor or a segment of the wiring harness is broken.

6. 6

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use the tractor's diagnostic menu or an Electronic Service Tool (EST) to clear the fault codes.

7. 7

   Replace if Necessary

   If the wiring, power, and grounds are all verified as good but the INST 12021 code immediately returns, the Auxiliary Controller has likely suffered an internal failure and must be replaced. Note: A new controller will require calibration via the dealer service tool.