Case IH 155 – Armrest Controller (ARU): Auto PTO switch data failed in the Armrest controller.

The data signal regarding the Auto PTO switch's position is missing, invalid, or failing to transmit properly over the tractor's data bus network. The system cannot verify whether the operator is commanding the Auto PTO to be on or off.

• Magnum
• MX Magnum Series (MX210, MX230, MX255, MX285)
• TG Series
• MXM Series (MXM120, MXM130, MXM140, MXM155, MXM175, MXM190)
• MXU Series
• Puma Series (Puma 155 Multicontroller)
• STX Steiger Series

1. 1

   Check for secondary codes such as ARM 1039 (PTO switch failure in the armrest) or PTO 1016 / PTO 1017, which indicate that the hard-wired connection between the PTO controller and the armrest controller has failed open.

2. 2

   Connect a diagnostic service tool to the tractor's Data Bus, go to the Monitor screen, select 'PTO OFF SW', and add it to your screen for testing.

3. 3

   Perform a toggle test by manually turning the Auto PTO switch on and off while watching the diagnostic screen. If the status changes, the switch works and the issue is a data bus error. If it does not change, the switch or its direct wiring has failed.

4. 4

   Inspect the PTO wiring from the armrest controller to the PTO controller, specifically checking for loose connectors, bent pins, and wire damage or deterioration.

1. 1

   Power down the tractor and disconnect the battery.

   This prevents electrical damage during service.

2. 2

   Disassemble the armrest console.

   Gain access to the Armrest Controller (ARU) and the rear of the Auto PTO switch.

3. 3

   Inspect the wiring harness and the connector plugging into the Auto PTO switch.

   Look for pushed-out pins, corrosion, or wire chafing. Clean the contacts if necessary.

4. 4

   Unclip or unscrew the faulty Auto PTO switch from the armrest bezel.

   Perform this step if the diagnostic toggle test failed and the wiring is intact, indicating the switch is internally contaminated or faulty.

5. 5

   Install the replacement Auto PTO switch.

   Securely reconnect the wiring harness.

6. 6

   Reassemble the armrest console.

7. 7

   Reconnect the battery and turn the ignition on.

8. 8

   Clear the stored fault code 155.

   Use the tractor's Pro 700 display or a connected diagnostic service tool.

9. 9

   Perform a functional test of the Auto PTO system.

   Ensure the PTO engages/disengages properly and the fault code does not return.