Case IH 18269 (518758.03, 518758.04) - ACML – ACML (Armrest Control Module): Rear Hitch Slip Control Potentiometer Circuit Error

Indicates an electrical circuit error involving the Rear Hitch Slip Control Potentiometer. 518758.03 (FMI 03) indicates the signal voltage is too high (short to power or open circuit), and 518758.04 (FMI 04) indicates the signal voltage is too low (short to ground or open circuit).

• MAXXUM T4E
• VESTRUM CVX
• Case IH Magnum Series: 235, 260, 290, 315, 340 (Series 4)
• Case IH Puma Series: 130, 145, 160, 165, 170, 180, 185, 195, 200, 210, 215, 225, 230 (including CVX / CVT models)
• Case IH Farmall Series: 115U Pro EP

1. 1

   Check the ACML for other active 5V reference codes (e.g., code 2054) to rule out a shared 5V supply issue.

2. 2

   Inspect the wiring harness and connector leading to the slip control potentiometer inside the armrest console for pinched wires, chafing, or loose pins.

3. 3

   If code is .04 (Voltage Too Low): Test the signal wire for a short to ground.

4. 4

   If code is .03 (Voltage Too High): Test the signal wire for a short to the 12V/5V supply or a complete open circuit.

5. 5

   Perform a sweep test by back-probing the potentiometer with a multimeter; slowly turn the dial and watch for a smooth, linear change in voltage or resistance.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Access the Armrest

   Carefully remove the retaining screws and lift the upper cover of the armrest console to access the internal control boards and potentiometers.

3. 3

   Disconnect the Sensor

   Locate the Rear Hitch Slip Control Potentiometer and unplug its electrical connector.

4. 4

   Verify Module Output

   Temporarily reconnect the battery and turn the key to the ON position. Use a multimeter to verify that the ACML is sending the correct 5V reference and ground to the connector.

5. 5

   Replace the Component

   If the wiring and module outputs are good, remove the retaining nut/clip holding the faulty potentiometer to the armrest bezel and install the replacement unit.

6. 6

   Reassembly

   Reconnect the electrical harness, secure the potentiometer, and reassemble the armrest console.

7. 7

   Calibration

   Reconnect the battery, turn the key ON, and clear the inactive fault codes. Depending on the specific tractor model (e.g., Puma CVT), you may need to enter the tractor's H1 calibration menu to perform an Electronic Draft Control (EDC) / Hitch calibration so the ACML can learn the new potentiometer's minimum and maximum voltage limits.