Case IH 1906 – VCM / UCM: VCM - 5Vref3 Sensor Supply Voltage Out Of Range

The 5-volt reference circuit #3 (5Vref3) is operating outside of its expected voltage parameters. This typically indicates a short to ground, a short to a 12V power source, an open circuit in the wiring harness, or an internally shorted sensor pulling the reference voltage down.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR130
• SR150
• SR175
• SV185
• SR200
• SR220
• SV250
• SV300
• TR270
• TR320
• TV380
• Steiger
• Magnum
• Puma

1. 1

   Verify the code 1906 is active using the machine's display or the Electronic Service Tool (EST).

2. 2

   Perform a Sensor Isolation Test: Disconnect the sensors on the 5Vref3 circuit one at a time. If the voltage returns to a normal 5V (or the code goes inactive) when a specific sensor is unplugged, that sensor is internally shorted.

3. 3

   Inspect the wiring harness for chafing, pinched wires, or corrosion. Look for areas where the 5Vref3 wire might be rubbing against the chassis (short to ground) or against a 12V supply wire (short to power).

4. 4

   Perform a Module Output Test: Disconnect the harness connector from the VCM/UCM. Probe the 5Vref3 output pin directly at the module. If the module fails to output 5V with the harness completely disconnected, the VCM/UCM itself has an internal failure.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes during repair.

2. 2

   Address the Faulty Component

   If a sensor failed: Replace the specific sensor identified during the isolation test. If the harness failed: Repair the damaged section of the wiring harness using automotive-grade wire and weather-sealed heat-shrink butt connectors, or replace the affected harness section entirely. If the VCM/UCM failed: Remove the mounting hardware and electrical connectors from the module. Install the new VCM/UCM.

3. 3

   Reprogramming

   If the VCM/UCM was replaced, you must connect the Electronic Service Tool (EST) to flash the module with the correct machine software and configure the machine's specific parameters.

4. 4

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use the EST or display to clear stored historical fault codes. Verify that code 1906 does not return.