Case IH 12111 – INST / INST2: Communications Lost with Automatic Temperature Controller

The machine's primary instrumentation system is no longer receiving data messages over the CAN bus network from the cab's Automatic Temperature Controller (ATC) module, which regulates the HVAC (heating, ventilation, and air conditioning) system.

• MX Magnum
• STX Steiger
• TG Series
• Steiger
• Puma series
• Axial-Flow AFX8010
• Axial-Flow 2588
• Axial-Flow 5088
• Axial-Flow 5130
• Axial-Flow 6088
• Axial-Flow 7088
• Axial-Flow 7120
• Axial-Flow 7130
• Axial-Flow 8120
• Axial-Flow 8230
• Axial-Flow 9010
• Axial-Flow 9240
• STX series

1. 1

   Verify the power supply (12V) and ground connections to the ATC module. A loss of power will cause the module to drop off the communication bus.

2. 2

   Inspect the 4-to-6 terminal factory connector on the ATC module for loose, corroded, or burnt pins.

3. 3

   Test the CAN bus communication lines between the ATC module and the INST controller for open circuits or shorts to ground.

4. 4

   Determine if the blower motor or A/C clutch operates in manual mode. If the system is completely dead, it points heavily toward a power failure at the module or a completely failed ATC module.

1. 1

   Disconnect power

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

2. 2

   Access the ATC module

   Remove the necessary interior cab trim panels (behind or under the seat) to access the ATC module and its wiring harness.

3. 3

   Repair connections

   If the diagnostic checks revealed a bad connection at the factory harness, clean the contacts. If a wire is burnt or a pin is loose, squeeze the contacts for a tighter fit or splice a bypass jumper wire for the damaged terminal.

4. 4

   Replace the module

   If the wiring, power, ground, and CAN lines all test perfectly but the 12111 code persists (meaning the module has internally failed and cannot broadcast on the network), remove the mounting hardware and replace the ATC Control Module.

5. 5

   Reassemble and clear codes

   Reconnect the battery, turn the key to the ON position, and use the instrumentation display or a diagnostic tool to clear the INST fault codes. Verify that the A/C and heater function correctly in both Auto and Manual modes.