Case IH 173 – TMF (Tractor Multi-Function) Controller or Transmission Controller: PTO Solenoid Circuit is failed shorted to ground when PTO is in the off state.

The control module is detecting a path to ground (a short circuit) on the Power Take-Off (PTO) solenoid's electrical circuit while the PTO switch is commanded to the 'OFF' position. This prevents the PTO from initializing safely, often disabling the PTO entirely to prevent uncommanded engagement.

• Magnum
• Case IH MX Series (MX210, 215, 235, 245, 275, 305, 340)
• Case IH Steiger Series (380, 480, 500, 530, 535, 550)
• Case IH Puma Series
• Case IH Maxxum Series

1. 1

   Check the PTO Switch in the Cab: Test the switch with a multimeter to ensure it isn't bleeding voltage to the 'no voltage' side when in the OFF position (e.g., showing 5V–7V on the OFF side).

2. 2

   Inspect the Wiring Harness: Trace the wiring from the TMF/Transmission controller to the PTO solenoid. Look for chafed insulation, pinched wires, or exposed copper touching the tractor chassis (ground).

3. 3

   Test the PTO Solenoid Coil: Disconnect the PTO solenoid connector and measure the resistance across the solenoid coil pins. Check for continuity between the power pin on the solenoid and the solenoid body/ground to see if it is internally shorted.

1. 1

   Disconnect Power

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

2. 2

   Locate the PTO Solenoid

   Locate the PTO control valve block, typically mounted on the rear frame or transmission housing.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a chafed wire shorting to the chassis, repair the wire using weather-sealed heat shrink connectors and re-loom the harness to prevent future rubbing.

4. 4

   Replace the PTO Solenoid

   If the solenoid is internally shorted, clean the area around the PTO solenoid valve to prevent dirt from entering the hydraulic system. Unplug the electrical connector, unscrew the retaining nut or mounting bolts holding the solenoid coil/cartridge, remove the old solenoid and install the new one (ensure the O-rings are lubricated with clean hydraulic oil before insertion). Torque to OEM specifications and reconnect the harness.

5. 5

   Replace the PTO Switch

   If the cab switch failed the multimeter test (leaking voltage), pop the switch out of the side console, disconnect the pigtail, and snap a new switch into place.

6. 6

   Clear Codes and Test

   Reconnect the battery, turn the key to the ON position, clear the stored TMF 173 fault code via the diagnostic display, and test the PTO engagement.