Case IH 1905 – UCM / VCM: 5Vref1 Sensor Supply Voltage Out Of Range

The controller has detected that the 5-volt reference 1 (5VREF1) circuit is operating outside of its normal voltage parameters. This condition is typically caused by a short to ground, a short to power, or an open circuit within the wiring harness or one of the sensors on that specific 5V circuit.

• skid steer
• Case SR175
• Case SR200
• Case SR220
• Case SR250
• Case SV250
• Case SV300
• Case TR320
• Case TV380
• Case IH Steiger
• Case IH Puma
• Case IH Magnum
• Early Riser series planters

1. 1

   Disconnect sensors on the 5VREF1 circuit one by one (e.g., load sensors, position potentiometers, pressure sensors). If voltage returns to 5V after unplugging one, that sensor is internally shorted.

2. 2

   Check the 5VREF1 circuit wiring harness for chafing, pinches, or exposed wires that could cause a short to ground or a short to a 12V power source.

3. 3

   Inspect the UCM/VCM connectors and sensor connectors for corrosion, bent pins, or moisture intrusion.

4. 4

   Disconnect the harness from the UCM/VCM and measure the voltage directly at the module's 5VREF1 output pins. If it is not outputting 5V, the module has failed.

1. 1

   Power Down

   Disconnect the battery or turn off the master disconnect switch before servicing the electrical system.

2. 2

   Repair/Replace the Faulty Component

   If a sensor was identified as shorted during diagnostics, replace the sensor. If the wiring harness is damaged, repair the broken/shorted wires or replace the affected harness section. If the UCM/VCM failed the output test, replace the control module.

3. 3

   Reassemble and Reconnect

   Reconnect all sensors, harnesses, and battery power.

4. 4

   Clear Codes

   Connect the Electronic Service Tool (EST) to the machine, clear the inactive 1905 fault code, and operate the machine to verify the error has been resolved and normal display readings have returned.