New Holland TMF 172 – TMF: PTO Solenoid Circuit is failed shorted to 12 Volts when PTO is in the off state.

The system has detected that the Power Take-Off (PTO) solenoid circuit is receiving 12 volts (B+) even though the PTO switch and system are commanded to the "OFF" state. This indicates an electrical short to power, which can cause the PTO to engage unexpectedly or prevent the system from operating safely.

• T6
• T7
• T8
• T9
• TM
• TS
• CR
• CX
• CR9090
• CX8080
• CX8090
• Magnum
• 235-340 Series 4
• Puma
• Maxxum

1. 1

   Test the resistance of the PTO solenoid coil at the PTO controller connector to see if the coil has failed internally (resistance too low).

2. 2

   Inspect the wiring circuit between the TMF controller and the PTO solenoid for a short to a +12V power source.

3. 3

   Determine if the TMF controller has an internal failure (such as an internal relay that is stuck in the 'ON' position).

1. 1

   Access the Components

   Turn off the tractor and locate the rear PTO solenoid and the TMF central controller (often located under the rear cab cover or right-hand console, depending on the model).

2. 2

   Disconnect and Inspect

   Disconnect the rear PTO solenoid connector and the inline harness connectors. Inspect the pins for corrosion, moisture, or melted plastic.

3. 3

   Test the Solenoid

   Using a digital multi-meter, measure the resistance across the PTO solenoid pins. If the resistance is out of specification (shorted/too low), the solenoid itself is faulty and must be replaced.

4. 4

   Test the Wiring Harness

   With the solenoid and controller disconnected, test the PTO signal wire for continuity to any 12-volt power source. If you read voltage or continuity to power, the wiring harness is chafed and shorting to a live wire. Repair the damaged section of the harness or replace the harness assembly.

5. 5

   Test the Controller

   If the solenoid resistance is correct and the wiring harness is not shorted, the fault is likely a stuck internal relay inside the TMF controller. The controller will need to be replaced and reprogrammed by a dealer.

6. 6

   Clear and Verify

   Once the faulty component is repaired or replaced, clear the TMF 172 error code via the diagnostic menu and test the PTO system for normal operation.