Case IH 12121 – INST: Communications Lost with Color Perfomance Monitor

The tractor or combine's main instrumentation system has lost its CAN bus communication link with the cab's primary color display (typically the AFS Pro 700 or older AFS Pro 600 monitor).

• MX Magnum
• Magnum (215, 245, 275, 305, 335)
• Steiger
• Puma
• Maxxum
• Optum
• Axial-Flow (5130, 6130, 7130, 7230, 7240, 8240, 9240)

1. 1

   Inspect the wiring harness connectors at the back of the AFS monitor and at the INST controller for moisture, corrosion, or aging pins

2. 2

   Verify that the AFS monitor is receiving proper voltage and has a solid ground connection

3. 3

   With the battery disconnected, measure the resistance across the CAN High and CAN Low pins at the monitor connector (should read around 60 ohms)

4. 4

   Inspect the fuse panel for any blown fuses related to the cab displays or the instrumentation controller

1. 1

   Disconnect Power

   Always disconnect the battery before servicing CAN bus wiring or removing control modules.

2. 2

   Clean and Secure Connections

   If moisture or corrosion was found during diagnostics, clean the affected pins with electrical contact cleaner. Apply a small amount of dielectric grease to prevent future moisture intrusion, and firmly reconnect the harness.

3. 3

   Repair Wiring

   If the CAN bus wires are chafed, pinched, or broken between the INST controller and the monitor, repair the wiring harness using OEM-approved splicing methods.

4. 4

   Monitor Replacement/Repair

   If the wiring is intact and the monitor is receiving power but still fails to communicate (or if the screen is physically damaged/unresponsive), the AFS monitor itself has an internal failure. You will need to either replace the monitor assembly or send it to an agricultural electronics specialist for internal board/touchscreen repair.

5. 5

   Reboot and Clear Codes

   Once the repair is made or the new monitor is installed, reconnect the battery, turn the key to the ON position, and use the diagnostic menu to clear the stored INST 12121 fault code.