Case IH 151 – TMF (Tractor Multi-Function Controller) or INST (Instrument Cluster / Gateway): Communications Lost with Transmission Controller

A CAN bus network issue where the tractor's network is no longer receiving data packets from the transmission control unit.

• Magnum
• Case IH MX Magnum Series
• Case IH TG Series
• Case IH Puma Series (e.g., Puma 125)

1. 1

   Verify battery voltage, as low voltage can cause control modules to drop off the CAN bus network

2. 2

   Check the fuse box for blown fuses or faulty relays that supply power to the Transmission Controller

3. 3

   Inspect the CAN bus wiring harness between the Armrest (TMF) controller, the Tractor ECU (Gateway), and the Transmission Controller for chafed wires, pinch points, or broken lines

4. 4

   Disconnect the Transmission Controller and inspect the pins for moisture, corrosion, or backed-out terminals

5. 5

   With the battery disconnected, measure the resistance across the CAN High and CAN Low pins (a healthy CAN bus should read approximately 60 ohms)

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery cable to prevent electrical shorts during testing.

2. 2

   Restore Power Supply

   If any fuses or relays powering the Transmission Controller were found blown or faulty during diagnostics, replace them.

3. 3

   Clean Connections

   Disconnect the main harness at the Transmission Controller. Clean the contacts thoroughly with electrical contact cleaner and ensure no moisture is trapped inside.

4. 4

   Repair Harness

   If the CAN High or CAN Low wires failed the continuity test, trace the harness to locate the break or short. Splice and repair the damaged wiring using proper weatherproof connectors.

5. 5

   Reconnect and Clear Codes

   Reconnect the Transmission Controller and the battery. Turn the key on and attempt to clear the fault codes.

6. 6

   Module Replacement

   If power, ground, and CAN bus wiring all test perfectly but the TMF 151 code remains active, the Transmission Controller itself has likely suffered an internal hardware failure and must be replaced. (Note: A new controller will require OEM dealer software to program and calibrate it to the tractor).