Case IH 1079.03 - ACML – ACML: Sensor Supply Voltage 1 - Voltage Above Normal, or Shorted to High Source

The 5-volt reference power supply circuit is measuring a voltage that is too high (typically above 5.2V to 5.5V), indicating that the 5V reference circuit is short-circuited to a 12V power source.

• VESTRUM CVX
• Case IH Magnum Series
• Case IH Maxxum Series
• Case IH Puma Series
• Case IH Steiger Series

1. 1

   Perform a sensor isolation test by disconnecting 5V sensors (hand throttle, clutch pedal, accelerator pedal, and enable pressure sensors) one at a time. If the fault goes inactive or voltage drops to 5V, the disconnected sensor is internally shorted.

2. 2

   Inspect the wiring harness connecting the ACML to the armrest controls for chafing, pinch points, or melted insulation where the 5V reference wire might rub against a 12V supply.

3. 3

   Inspect the main connectors at the ACML for corrosion, moisture ingress, or bent/pushed-out pins that could bridge a 12V pin to the 5V reference pin.

4. 4

   Perform a module output test by disconnecting the sensor harness completely from the ACML and measuring voltage directly at the 5V reference pin. If it outputs 12V, the ACML has an internal short.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Armrest

   Remove the necessary trim panels on the multicontroller armrest to access the ACML and the affected sensor wiring.

3. 3

   Repair the Short

   If a sensor failed, replace the internally shorted potentiometer/sensor. If the harness failed, cut out the damaged section and repair it using OEM-approved splice connectors and marine-grade heat shrink, or replace the affected armrest sub-harness. If the ACML failed, unbolt the module, disconnect the main harness plugs, and install the replacement ACML.

4. 4

   Reassembly and Verification

   Reconnect the battery. Turn the key to the ON position and use a multimeter to verify the reference circuit is now reading a steady ~5.0V.

5. 5

   Calibration

   If the ACML was replaced, connect the CNH Electronic Service Tool (EST) to clear the historical fault codes and push the necessary configuration/calibration files to the new armrest module.