Case IH 4040 – Arm Rest Module (ARU) / DV Module: Supply voltage - too low (DV module only) / ARU Supply Voltage – too low (<8V)

The electrical voltage being supplied to the Arm Rest Unit (ARU) / DV Module has dropped below the minimum operating threshold of 8 Volts. When the voltage drops this low, the module cannot reliably process inputs from the operator controls (like the throttle, hitch controls, or remote valves) or communicate properly over the CAN bus network.

• Maxxum
• Puma series
• Magnum series
• Steiger series
• CT series

1. 1

   Test the main battery voltage and alternator output to ensure the tractor's electrical system is producing a healthy 12V–14V.

2. 2

   Locate the cab/armrest power supply fuses in the main fuse panel and check for blown fuses, loose seating, or corrosion on the fuse legs.

3. 3

   Inspect the wiring harness routing from the cab floor up into the armrest console for pinched, chafed, or stretched wires caused by seat/armrest movement.

4. 4

   Disconnect the main harness connector at the ARU/DV module and perform a pin-point voltage test at the power supply pins with the key ON (below 8V indicates wiring/ground issues; above 8V indicates internal module failure).

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical shorts during repair.

2. 2

   Access the Module

   Remove the plastic trim panels on the armrest console to expose the Arm Rest Module (ARU) and its wiring harness.

3. 3

   Clean Connections

   Disconnect the ARU module connectors. Spray the pins and receptacles with a high-quality electrical contact cleaner. Check for pushed-back pins or moisture intrusion.

4. 4

   Repair Wiring

   If the diagnostic checks revealed a voltage drop, trace the power and ground wires back to the cab distribution panel. Repair any damaged wire sections using solder and heat-shrink tubing, and clean the cab ground strap connections.

5. 5

   Replace the Module

   If the wiring is perfectly intact and delivering full battery voltage to the module, the ARU has failed internally. Unbolt the old module, install the replacement ARU, and reconnect the harness.

6. 6

   Reassemble and Test

   Reconnect the battery. Turn the key to the ON position and verify that fault code 4040 changes from 'Active' to 'Stored/Inactive'. Clear the code using the tractor's diagnostic menu or a service tool.