Case IH 156 – Armrest Controller: Auto PTO switch is stuck ON in the Armrest Controller

The controller is receiving a continuous, uninterrupted "ON" signal from the Auto PTO switch, which typically points to a mechanically jammed button, an internal short circuit within the switch itself, or a short to power in the switch's wiring harness.

• Magnum
• MX Magnum
• TG Series
• Steiger
• Puma
• Maxxum
• MXU Series
• MXU100
• MXU110
• MXU115
• MXU125
• MXU135
• Magnum 235-340
• T8 Series
• TS-A Series
• TS110
• TS115A
• TS125

1. 1

   Inspect the Auto PTO switch on the armrest console to see if the button is physically jammed, sticking due to dirt/debris, or failing to spring back to its neutral position.

2. 2

   Disconnect the switch and use a multimeter to test for continuity. The switch should only show continuity when actively pressed. If it shows a closed circuit continuously, the switch has failed internally.

3. 3

   If the switch tests fine, inspect the wiring harness between the armrest switch and the TMF controller for a short to a 12V power source.

1. 1

   Disconnect battery

   Power down the tractor and disconnect the negative battery cable.

2. 2

   Access switch panel

   Remove the retaining screws/clips on the armrest control console to access the underside of the switch panel.

3. 3

   Disconnect switch harness

   Locate the Auto PTO switch and disconnect its electrical harness connector.

4. 4

   Remove faulty switch

   Depress the retaining tabs on the sides of the faulty switch and push it up and out of the armrest dashboard.

5. 5

   Install new switch

   Snap the new OEM Auto PTO switch into the panel.

6. 6

   Reconnect harness

   Reconnect the electrical harness to the new switch.

7. 7

   Reassemble console

   Reassemble the armrest console housing.

8. 8

   Verify repair

   Reconnect the battery, turn the ignition on, and verify that fault code 156 has cleared and the Auto PTO engages/disengages properly.