Case IH 13003 – UCM (Universal Control Module) or main Electronic System controller: Reference voltage 5VREF2 - voltage too low

The 5-volt reference circuit (circuit number 2) is experiencing a voltage drop below the acceptable operational threshold. This is typically caused by a short to ground within the wiring harness, a failed sensor that is internally shorted and pulling the reference voltage down, or an internal failure within the control module.

• MAXXUM T4E
• Case IH Puma series tractors
• Case IH Magnum series tractors (MX210, MX230, MX255, MX285)
• Case IH Maxxum series tractors
• Case IH Axial-Flow Combines (7230, 8230, 9230)

1. 1

   Sensor Disconnect Test: Disconnect the sensors on the 5VREF2 circuit one at a time. Monitor the fault codes or use a multimeter to check the voltage at the UCM output pin. If the voltage returns to 5V (or the code changes to 13004), the sensor you just disconnected is internally shorted.

2. 2

   Harness Inspection: If all sensors on the circuit are disconnected and the voltage remains low, check the wiring harness for chafing, pinched wires, or melted insulation causing a short to ground.

3. 3

   UCM Pin Check: Disconnect the harness directly at the UCM and measure the voltage at the 5VREF2 output pin (e.g., Connector X-950, Pin 03 on some Magnum models). If the UCM does not output 5V with the harness completely disconnected, the UCM itself has an internal power supply fault.

1. 1

   Locate components

   Turn off the machine and locate the UCM and the sensors sharing the 5VREF2 circuit for your specific model.

2. 2

   Perform sensor disconnect test

   Perform the sensor disconnect test outlined above to isolate the shorted component.

3. 3

   Replace faulty sensor

   If a sensor is found to be shorted, remove the faulty sensor and install a replacement.

4. 4

   Repair or replace wiring harness

   If the harness is shorted to ground, trace the wire from the UCM to the sensors. Repair the damaged section of the wire using heat-shrink connectors, or replace the affected harness section.

5. 5

   Replace UCM

   If the UCM is failing to output the 5V reference internally, replace the UCM.

6. 6

   Verify repair

   Reconnect all components, turn the key on, and clear the fault codes to verify the repair.