Case IH 9152 – UCM: Bus-Warn at CAN-Bus No.1

A control module has lost communication on the primary CAN Bus network (CAN-Bus No. 1) for more than 5 seconds. Modules operate in isolation and cannot receive or send critical data, resulting in limp-home mode activation or total system shutdown.

• skid steer
• Steiger
• Magnum
• Maxxum
• Farmall
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Excavators
• Wheel Loaders

1. 1

   Check battery voltage and ensure it does not drop excessively during cranking, which can cause the ECU to log a communication timeout.

2. 2

   Inspect the CAN bus wiring harness for physical damage, chafing, or internal breaks, particularly near the armrest or articulation points.

3. 3

   Inspect the UCM and ECU connectors for corrosion, pushed-back pins, or moisture ingress.

4. 4

   Test the CAN bus resistance across the CAN High and CAN Low pins. A healthy network should read 60 Ohms. If it reads 120 Ohms, one terminating resistor is missing or damaged. If it reads open, there is a broken wire.

1. 1

   Disconnect Power

   Disconnect the negative battery terminal before servicing the electrical system.

2. 2

   Repair Wiring

   If a break or short is found in the CAN bus wiring, splice and repair the damaged section using proper CAN bus repair connectors, or replace the affected harness section entirely.

3. 3

   Replace Terminating Resistor

   If the resistance test showed 120 Ohms, locate the faulty terminating resistor (often located at the ends of the harness or near the engine bay/rear cover) and replace it.

4. 4

   Replace the UCM

   If the wiring and resistors are perfectly intact, the UCM itself may have an internal short or failure. Remove the UCM cover and mounting bracket, disconnect the UCM interface wire harness, and install the replacement UCM.

5. 5

   Recalibrate

   After replacing a UCM, the new module will likely need to be flashed/programmed with the machine's specific configuration using the EST (Electronic Service Tool).