Case IH 44.00 - ACML – ACML: Error on voltage 5Vref2 supply detected

This fault indicates a critical voltage irregularity (either a short to ground or a short to power) on the 5Vref2 (5-Volt Reference 2) circuit. The system's safety logic automatically switches the 5Vref2 supply OFF to prevent module damage, causing all sensors and devices relying on this circuit to lose power and go into an error state.

• MAXXUM T4E
• VESTRUM CVX
• Puma
• Magnum
• Steiger
• Optum

1. 1

   Turn the key switch to the ON position and monitor the active diagnostic codes using an electronic service tool or the tractor's display

2. 2

   Disconnect sensors powered by the 5Vref2 circuit one at a time (e.g., armrest position sensors, draft pin sensors, spool valve potentiometers)

3. 3

   Wait about 30 seconds after disconnecting each sensor to see if the fault code changes from Active to Inactive, which isolates an internally shorted sensor

4. 4

   Inspect the wiring harness for chafing, pinched wires, or melted insulation if all sensors are disconnected and the fault remains active

5. 5

   Inspect the ACML connectors for bent pins, water intrusion, or corrosion that could bridge the 5V pin to a ground pin

1. 1

   Resolve the Short

   If a sensor is shorted: Obtain a replacement sensor. Before fully installing it mechanically, plug it into the electrical connector and verify that the 5Vref2 fault code remains inactive. If the harness is shorted: Repair the chafed wire using OEM-approved splicing methods and heat-shrink tubing, or replace that section of the harness.

2. 2

   Replace the ACML (Last Resort)

   If the wiring harness tests perfectly for continuity and lacks any shorts to ground/power, and all sensors are unplugged but the module still refuses to output 5 volts, the ACML's internal 5V regulator is burnt out. Replace the Armrest Control Module.

3. 3

   Reassembly

   Reconnect all sensors.

4. 4

   Clear Codes

   Use the electronic service tool or the tractor's diagnostic menu to clear the logged 44.00 fault code and any secondary sensor codes that were triggered during your unplugging tests.

5. 5

   Calibration

   If a position sensor or the ACML was replaced, you must perform the armrest and spool valve calibrations via the tractor's display menu.