John Deere ACU523960.31 – ACU: Inoperative Operator or Faulty Sensor

The Armrest Control Unit (ACU) has detected that the operator is not in the seat when required for a specific machine function. This diagnostic trouble code indicates either that the operator has left the seat during active operation, or that there is a malfunction within the operator presence sensor system or its wiring.

• 7630
• 7730
• 7830
• 7930
• 7R Series
• 8R Series
• 9R Series
• 7210
• 7410
• 7510
• 9760

1. 1

   Verify operator action: Ensure the operator is properly seated during machine operation (the most common cause).

2. 2

   Perform a system reset by cycling the tractor's main power via the key switch.

3. 3

   Ensure the transmission is in 'Park'. In some cases, depressing the brake or clutch pedal may be required to clear the code.

4. 4

   Perform an Operator Presence System Check: Start engine with park brake engaged and the multifunction handle in neutral, engage a function, briefly lift off seat (less than 2 seconds) and sit back (function should continue). Remain seated for 10 seconds, then lift completely off (function should stop within 5 seconds). It should not resume when you sit back down until the function is re-engaged.

5. 5

   Visually inspect the wiring and connectors for the seat presence switch (located under the seat) for damage, corrosion, or loose connections.

1. 1

   Prepare machine for service

   Ensure the tractor is on a level surface, the parking brake is engaged, and the engine is off. Disconnect the battery.

2. 2

   Access the switch

   Locate the operator presence switch within the seat cushion. Access may require removing the seat or seat trim panels.

3. 3

   Disconnect wiring

   Locate the electrical connector for the seat switch and disconnect it.

4. 4

   Remove the old switch

   Remove the faulty switch. The method of removal depends on the specific seat design (it may be held in place by clips or integrated into a bar assembly).

5. 5

   Install the new switch

   Install the new operator presence switch, ensuring it is correctly seated.

6. 6

   Reconnect and reassemble

   Reconnect the electrical connector and reassemble any trim or components that were removed.

7. 7

   Test the system

   Reconnect the battery and perform the Operator Presence System Check to verify the repair.