Case IH 14903 – Main Vehicle Controller / Instrument Cluster (INST) / Transmission Controller: SCM controller missing (GA 12x12 only)

The main vehicle controller or instrument cluster has lost communication with the Small Control Module (SCM) over the tractor's CAN bus network.

• Maxxum
• Puma
• Farmall
• MXM

1. 1

   Check fuses that supply power to the SCM (Fuse 10, Fuse 14, and Fuse 20 depending on layout)

2. 2

   Inspect the SCM main connectors (e.g., C125) for loose pins, pushed-out terminals, moisture, or corrosion

3. 3

   Verify the SCM is receiving steady 12V power and has a clean ground connection using a multimeter

4. 4

   Test the CAN High and CAN Low lines at the SCM connector for continuity back to the main controller, and verify network resistance is approximately 60 ohms with the battery disconnected

1. 1

   Power Down

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

2. 2

   Access the SCM

   Locate the Small Control Module (location varies by cab configuration, often found under the right-hand console or near the fuse/relay panel).

3. 3

   Harness Inspection

   Disconnect the wiring harness from the SCM. Inspect the wiring for chafing, breaks, or shorts to ground, particularly where the harness routes near the transmission housing.

4. 4

   Clean Contacts

   If corrosion is present, clean the harness terminals with electrical contact cleaner and apply dielectric grease. Reconnect and test the tractor to see if the code clears.

5. 5

   Replace the Module

   If power, ground, and CAN wiring are all intact but the module remains unresponsive (missing), the SCM has failed internally and must be replaced.

6. 6

   Reconfiguration

   Install the new SCM. Depending on the tractor model, you may need to enter the tractor's H-Menu (diagnostic/calibration menu) to configure the new module or calibrate the transmission clutches and electronic draft control (EDC) so the main controller recognizes the new SCM.