New Holland NH 4009 – ARU (Arm Rest Module / Armrest Control Unit): Signal of Aux-stick (AUX3) out of range low

The voltage signal coming from the 3rd auxiliary axis (AUX3) on the armrest joystick has fallen below the minimum acceptable threshold. This typically points to a short to ground, an open circuit in the wiring harness, or a complete failure of the potentiometer/Hall-effect sensor inside the joystick.

• T6 series
• T7 series
• T8 series
• T9 series
• T6000 series
• T7000 series
• TG series

1. 1

   Check for related code NH 4040 (ARU Supply Voltage - Too Low) which indicates a broader power supply issue rather than a failed joystick.

2. 2

   Inspect the wiring harness and connectors beneath the armrest console for loose pins, backed-out wires, or corrosion.

3. 3

   Test sensor voltage using a multimeter to verify that the joystick is receiving the correct 5V reference voltage and has a solid ground.

4. 4

   Perform a sweep test by back-probing the AUX3 signal wire and slowly moving the joystick. The voltage should smoothly scale between 0.5V and 4.5V. If it stays near 0V, the potentiometer/sensor is shorted or dead.

1. 1

   Disconnect Power

   Turn off the tractor key and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Joystick

   Remove the retaining screws on the armrest control panel/console to expose the underside of the multi-function joystick.

3. 3

   Disconnect the Harness

   Unplug the main electrical connector from the joystick assembly.

4. 4

   Replace the Component

   Depending on the specific joystick revision, the potentiometers may be individually replaceable, or the entire joystick assembly may need to be swapped. Remove the mounting bolts securing the joystick to the armrest frame and extract the unit.

5. 5

   Install the New Part

   Seat the new joystick or potentiometer, secure the mounting hardware, and plug in the electrical connector.

6. 6

   Reassemble and Calibrate

   Reinstall the armrest covers and reconnect the battery. Turn the key on and use the tractor's IntelliView monitor (or a dealer diagnostic tool) to perform a joystick calibration procedure, ensuring the ARU learns the new minimum and maximum voltage ranges for the AUX3 axis.

7. 7

   Clear Codes

   Clear the NH 4009 inactive code and test hydraulic functions.