Case IH 2272 (518705.10) - DEC – Universal Control Module 1 (UCM1): CAN 2 - PB_UCM1_27 Absent on CAN2

Indicates that a specific expected data message (PB_UCM1_27) is missing or absent from the CAN 2 bus network. The module logging this fault has lost communication with the Universal Control Module 1 (UCM1) over the CAN 2 network.

• MAXXUM T4E
• VESTRUM CVX
• Axial-Flow Flagship Series 7230
• Axial-Flow Flagship Series 8230
• Axial-Flow Flagship Series 9230
• Axial-Flow Flagship Series 7240
• Axial-Flow Flagship Series 8240
• Axial-Flow Flagship Series 9240
• Axial-Flow Flagship Series 7250
• Axial-Flow Flagship Series 8250
• Axial-Flow Flagship Series 9250
• AFS Connect Magnum (180-380 models)
• Steiger AFS Connect
• Puma CVT
• Maxxum series
• Patriot Series 3250
• Austoft 8800
• Austoft 9900

1. 1

   Check for Multiple Faults: Connect the Case IH Electronic Service Tool (EST) to the diagnostic port (CAN 2 is typically accessed via the secondary diagnostic port, pins C and D). If multiple modules are reporting 'Absent on CAN 2' faults, the entire CAN 2 bus is likely down (shorted or open).

2. 2

   Symptom Check: On many Case IH machines, if the UCM1 goes offline, the system will default to an 'Emergency Lighting Mode' (beacons, low beams, and position lights will activate). If LEDs are flashing, it is a CAN communication issue; if they are not, it is likely a UCM1 power/ground issue.

3. 3

   CAN Bus Resistance Test: Disconnect the machine's batteries. Measure the resistance across the CAN 2 bus (Pins C and D on the diagnostic connector). A healthy CAN bus should read exactly 60 ohms. 120 ohms indicates an open circuit or a missing terminating resistor. 0 ohms indicates a short circuit in the CAN wiring.

4. 4

   Power and Ground Verification: Check the cab fuse box and relays supplying power to the UCM1. Verify 12V power and solid ground directly at the UCM1 bulkhead connectors.

1. 1

   Isolate the CAN 2 Bus

   If the resistance test failed, begin disconnecting modules on the CAN 2 bus one by one. If the resistance returns to 60 ohms after unplugging a specific module, that module is internally shorted.

2. 2

   Inspect Wiring and Connectors

   Inspect the main cab interface bulkhead connectors and the wiring harness leading to the UCM1. Look for pushed pins, corrosion, or wire chafing, which are common in agricultural environments. Repair any damaged CAN High (Yellow) or CAN Low (Green) wires.

3. 3

   Check Terminating Resistors

   Locate the CAN 2 terminating resistors (often located in the cab roof or near the UCM1). Ensure they are plugged in and measure 120 ohms individually. Replace if faulty.

4. 4

   Replace UCM1

   If wiring, power, ground, and CAN resistance are all within specification, the UCM1 internal CAN transceiver has likely failed. Replace the UCM1 module.

5. 5

   Software Calibration

   After replacing the UCM1, connect the EST laptop and flash the module with the latest software version (e.g., V33.33.0.0 or newer for combines, V52.3.0.0 for Magnums).