Case IH 43.00 - ACML – ACML: 5VREF1 Supply Switched OFF

The fault indicates a critical issue on the 5VREF1 (5-Volt Reference 1) circuit. When the system detects a voltage out of range (caused by a short to ground, a short to 12V power, or a failed sensor drawing excessive current), the module's internal protection logic activates and switches the 5VREF1 supply OFF to prevent permanent damage. This causes all connected devices on that circuit to lose power simultaneously.

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

1. 1

   Perform a sensor isolation (drop-out) test by disconnecting sensors powered by the 5VREF1 circuit one at a time (e.g., powershift throttle, hitch position potentiometer) to see if the 5V supply returns to normal, indicating an internally shorted sensor.

2. 2

   Inspect the armrest wiring harness for chafing, pinched wires, or exposed copper shorting to the metal frame of the armrest or cab.

3. 3

   Perform a module output test by disconnecting the main harness connector from the ACML and measuring the voltage directly at the 5VREF1 output pin. If it does not output 5V, the ACML has an internal failure.

1. 1

   Power Down

   Turn off the ignition and disconnect the battery ground cable before performing electrical repairs.

2. 2

   Access the Armrest

   Remove the plastic covers on the right-hand Multicontroller armrest to expose the ACML and the sensor wiring harness.

3. 3

   Repair the Short

   If a sensor was identified as shorted during the diagnostic checks, remove and replace the faulty sensor. If the harness is damaged, repair the broken/shorted wire using appropriate heat-shrink connectors and re-wrap the harness with anti-chafing tape.

4. 4

   Replace the ACML

   If the module itself is internally shorted, unbolt the ACML from the armrest frame, disconnect the multi-pin connectors, and install the new module.

5. 5

   Reprogramming

   If the ACML is replaced, the new module will likely need to be flashed and calibrated to the tractor's specific configuration using the CNH Electronic Service Tool (EST).

6. 6

   Clear Codes

   Reconnect the battery, turn the key ON, and use the diagnostic tool to clear the inactive codes and verify the 5VREF1 voltage is stable.