Case IH 3733 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): PTO switch : Diagnostic fault check for min error of COM message

This code indicates a communication (COM) error regarding the Power Take-Off (PTO) switch. Specifically, the control module is detecting that the signal or CAN bus message from the PTO switch has fallen below the minimum expected threshold (min error). This typically points to an open circuit, a short to ground in the switch wiring, a failed internal contact within the PTO switch, or a CAN bus communication glitch between the cab controller and the engine.

• Magnum MX180
• Magnum MX200
• Magnum MX220
• Magnum MX240
• Magnum MX270
• Maxxum MX80C
• Maxxum MX90C
• Maxxum MX100
• Maxxum MX110
• Maxxum MX120
• Maxxum MX135
• Maxxum MX150
• Maxxum MX170
• 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 to MXM190
• MXU100 to MXU135

1. 1

   Visually inspect the physical PTO switch in the cab to see if the push/pull mechanism feels loose, gritty, or fails to click into the engaged/disengaged positions.

2. 2

   Remove the console trim to access the back of the PTO switch and inspect the wiring harness and connector for melted plastic, corrosion, or backed-out pins.

3. 3

   Test the switch contacts for continuity/resistance using a multimeter. The switch should show clear continuity when engaged and an open circuit when disengaged (or vice versa). High resistance or no continuity indicates internal failure.

4. 4

   Check the CAN bus wiring harness leading from the cab console to the ECU for chafing or pinch points, as a short to ground on the signal wire will trigger a 'min error' fault.

5. 5

   Check for related codes, such as code 3734 (non-plausibility of COM message) or other EDC communication codes. Multiple COM codes may indicate a main CAN bus wiring fault rather than a switch issue.

1. 1

   Preparation

   Park the tractor on a level surface, turn off the engine, engage the parking brake, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access the Switch

   Carefully pry up or unscrew the side console or dashboard trim panel that houses the yellow PTO engagement switch.

3. 3

   Disconnect the Harness

   Reach behind the panel and depress the locking tab on the electrical pigtail connected to the PTO switch. Pull the connector free.

4. 4

   Remove the Old Switch

   Squeeze the plastic retaining tabs on the sides of the switch body inward and push the switch up and out through the top of the console panel.

5. 5

   Install the New Switch

   Route the new OEM switch through the top of the console panel and press down until the retaining tabs click securely into place.

6. 6

   Reconnect

   Plug the electrical harness back into the switch, ensuring the locking tab clicks.

7. 7

   Reassembly

   Reinstall the console trim panel and secure any screws. Reconnect the negative battery cable.

8. 8

   Clear Codes and Test

   Turn the ignition key to the ON position. Use a diagnostic scan tool to clear fault code 3733 from the EDC. Start the tractor and test the PTO engagement and disengagement to ensure the code does not return and the safety interlocks function correctly (e.g., the tractor should shut down the PTO if the operator leaves the seat).