Case IH 14018 – ICU (Instrument Control Unit): GOV Off Line

The Governor (GOV) / Engine Control Module (ECM/ECU) has lost communication with the machine's Controller Area Network (CAN bus). The system is no longer receiving CAN messages or speed/pressure data from the engine controller.

• Magnum
• Steiger T4B
• Case IH Magnum 235
• Case IH Magnum 260
• Case IH Magnum 290
• Case IH Magnum 315
• Case IH Magnum 340
• Case IH Magnum 370 (Series 4)
• Case IH STX Steiger 350 to 600

1. 1

   Check Fuses: Verify all fuses related to the engine controller and CAN bus. A blown fuse can cut power to the GOV, causing it to drop offline.

2. 2

   CAN Bus Resistance Test: With the key OFF and the battery disconnected, measure the resistance between the CAN High (typically yellow) and CAN Low (typically green) wires at the diagnostic connector or module harness. A healthy CAN bus should read exactly 60 ohms. 120 ohms indicates a failed terminator or open circuit; infinite resistance indicates both terminators are bad or the main harness is severed.

3. 3

   Power and Ground Check: Disconnect the harness at the GOV (Engine ECU). Check for proper voltage on the power supply wires (red wires should have full battery voltage) and check the ground wires (black wires should have 0 ohms to chassis ground).

1. 1

   Power Down

   Turn off the key, ensure all UCM external activations are shut down, and disconnect the battery to prevent electrical spikes.

2. 2

   Inspect the Harness

   Visually trace the CAN bus wiring harness between the ICU (cab/dash area) and the GOV (engine block). Look for chafing, pinched wires, or melted insulation, particularly where the harness routes from the cab to the engine bay.

3. 3

   Clean and Reseat Connectors

   Disconnect the main harness connectors at the GOV and the ICU. Inspect the pins for corrosion, moisture, or pushed-back terminals. Clean with contact cleaner, apply dielectric grease, and firmly reseat the connectors.

4. 4

   Replace Terminating Resistors

   If your diagnostic resistance test yielded 120 ohms, locate and replace the faulty CAN bus terminating resistor on the affected end of the network.

5. 5

   Test the Machine

   Reconnect the battery, turn the key on, and use the electronic service tool (EST) or the tractor's diagnostic display to clear the inactive codes.

6. 6

   Module Replacement

   If the wiring, terminators, power, and ground are all 100% verified and the 60-ohm CAN resistance is present, the GOV (Engine Control Module) itself has likely suffered an internal hardware failure and must be replaced or reflashed by a dealer.