New Holland 173 – TMF: PTO Solenoid Circuit Shorted to Ground

The Tractor Multi-Function (TMF) controller has detected an electrical short to ground in the Power Take-Off (PTO) solenoid circuit when the PTO is commanded to the 'off' state. This indicates that the electrical current controlling the PTO solenoid is finding an unintended path to the tractor's chassis or ground, which can prevent the PTO from disengaging correctly or cause other electrical system issues.

• T4
• T5
• T6
• T7
• T8
• 5640
• 6640
• 7740
• 7840
• 8240
• 8340
• TS100
• TS115A
• Workmaster
• Powerstar
• TD5
• Magnum
• Puma
• Maxxum
• Farmall

1. 1

   Inspect the wiring harness leading from the TMF controller to the PTO solenoid for any signs of chafing, melting, pinched wires, or corrosion on the connectors, paying close attention to the connector at the PTO solenoid itself

2. 2

   Check the PTO engagement switch in the cab for proper operation and continuity using a multimeter, as a faulty switch can sometimes mimic a solenoid or wiring issue

3. 3

   Test the PTO solenoid for an internal short by disconnecting it and measuring the resistance between its electrical terminals and the tractor's chassis ground; a low resistance reading indicates an internal short

4. 4

   Isolate the circuit by disconnecting the PTO solenoid and checking if the fault code disappears; if it does, the issue is likely with the solenoid, but if it remains, the short is in the wiring harness between the controller and the solenoid connector

5. 5

   Check for low battery voltage, as it can sometimes cause erratic behavior in electronic control modules and trigger 'ghost' codes; ensure the battery and charging system are functioning correctly

1. 1

   Safety First

   Ensure the tractor is on a level surface, the engine is off, the parking brake is engaged, and the wheels are chocked. Disconnect the battery to prevent electrical shorts during the repair.

2. 2

   Locate the PTO Solenoid

   The PTO solenoid is typically located on the rear of the tractor, often on a hydraulic valve block near the rear differential or PTO housing. On some models, it may be accessible from underneath or by removing a protective cover.

3. 3

   Disconnect and Inspect

   Disconnect the electrical connector from the solenoid. Inspect the connector terminals for corrosion or damage and clean or repair as necessary.

4. 4

   Test the Solenoid

   With the solenoid disconnected, use a multimeter to check for a short to ground. If a short is confirmed, the solenoid must be replaced.

5. 5

   Remove the Old Solenoid

   Remove the retaining nut on the valve stem and slide the solenoid coil off the stem. Be prepared for potential hydraulic oil leakage when removing components from the valve block.

6. 6

   Install the New Solenoid

   Slide the new solenoid onto the valve stem and secure it with the retaining nut. Ensure it is seated correctly.

7. 7

   Reconnect and Secure

   Reconnect the electrical connector, ensuring it is clean and makes a solid connection. Secure any related wiring harnesses away from moving parts or sources of heat and abrasion.

8. 8

   Reassemble and Test

   Reconnect the battery. Start the tractor and check for any active fault codes. Test the PTO engagement and disengagement functions multiple times to ensure the repair was successful.