Case IH 3731 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): PTO switch : Diagnostic fault check for signal error of COM message

This code indicates a communication (COM) or signal error originating from the Power Take-Off (PTO) switch. The control module is receiving an implausible signal, an interrupted signal, or is failing to communicate with the switch over the CAN bus network.

• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 135
• Maxxum 140
• Maxxum 145
• Maxxum 150
• Puma 115
• Puma 125
• Puma 140
• Puma 155
• Puma 165
• Puma 180
• Puma 195
• Puma 210
• Farmall 95U
• Farmall 105U
• Farmall 110U
• Farmall 115U
• Farmall 120U
• MXM120
• MXM130
• MXM140
• MXM155
• MXU100
• MXU135
• CX50 through CX110
• MC80 through MC130

1. 1

   Inspect the PTO switch on the side console for physical damage, sticking, or failure to physically click into the engaged/disengaged positions.

2. 2

   Remove the console trim to access the back of the switch and inspect the wiring harness and connector for pushed-out pins, corrosion, or moisture.

3. 3

   Test the switch contacts with a multimeter to ensure it is properly opening and closing the circuit when actuated.

4. 4

   Check the CAN bus communication lines between the switch harness and the EDC/ECU for continuity or shorts to ground.

1. 1

   Power Down

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

2. 2

   Access the Switch

   Carefully pry up or unscrew the side console trim panel where the PTO switch is mounted.

3. 3

   Disconnect

   Unplug the electrical wiring harness connector from the bottom of the PTO switch.

4. 4

   Remove the Switch

   Depress the retaining tabs on the sides of the switch body and push it upward through the console panel to remove it.

5. 5

   Install the New Part

   Snap the new OEM PTO switch into the console panel until the retaining tabs click into place.

6. 6

   Reconnect

   Plug the wiring harness connector back into the switch, ensuring the locking tab engages.

7. 7

   Reassemble

   Reinstall the console trim panel.

8. 8

   Clear Codes

   Reconnect the battery. Use a CNH diagnostic tool (EST) to clear the 3731 fault code from the EDC.

9. 9

   Test

   Start the tractor and engage/disengage the PTO to verify the repair and ensure the code does not return.