Case IH 157 – TMF (Tractor Multi-Function) Controller: PTO remote fender switch short circuit

The controller has detected a short circuit in the electrical circuit of the rear fender-mounted Power Take-Off (PTO) switch. This typically means the wiring has rubbed through its insulation and is grounding out against the tractor frame, wires have melted together, or the switch itself has failed internally due to moisture or physical damage.

• Magnum
• CX Series
• CX50
• CX60
• CX70
• CX80
• CX90
• CX100
• MX Series
• MX80C
• MX90C
• MX100
• MX110
• MX120
• MX135
• MX150
• MX170
• MX Magnum Series
• MX180
• MX200
• MX210
• MX220
• MX230
• MX240
• MX255
• MX270
• Puma Series
• 115
• 125
• 130
• 140
• 145
• 155
• 165
• 180
• 195
• 210
• Maxxum Series
• Steiger Series

1. 1

   Visually inspect the PTO switch on the rear fender for physical damage, cracked housing, or heavy moisture/dirt ingress.

2. 2

   Trace the wiring harness from the fender switch back to the TMF controller. Look for pinched wires, chafing against the fender or chassis, or melted insulation.

3. 3

   Disconnect the switch and inspect the connector pins for corrosion, water intrusion, or bent pins.

4. 4

   Test the switch for internal continuity with a multimeter. If the switch shows a closed circuit (continuity) across the contacts without the button being pressed, it is internally shorted.

5. 5

   Test the harness side for a short to ground or a short to 12V power.

1. 1

   Safety First

   Turn off the tractor, remove the key, and disconnect the battery to prevent further electrical damage or accidental PTO engagement.

2. 2

   Access the Switch

   Locate the faulty PTO remote switch on the rear fender.

3. 3

   Disconnect

   Reach behind the fender (or remove the protective inner fender liner if equipped) and unplug the electrical harness connector from the back of the switch.

4. 4

   Remove the Switch

   Remove the switch clamp or retaining nut holding the switch to the fender housing. Pull the old switch out of the mounting hole.

5. 5

   Repair Wiring (If Applicable)

   If your diagnostic checks revealed chafed wires on the harness, cut out the damaged section and repair it using automotive-grade wire and weatherproof heat-shrink tubing.

6. 6

   Install New Switch

   Insert the new PTO switch into the fender hole. Secure it using the switch clamp or retaining nut.

7. 7

   Reconnect

   Plug the electrical harness back into the switch, ensuring the weather seal is intact and the connector clicks into place.

8. 8

   Test

   Reconnect the battery. Turn the ignition on and clear the stored fault codes using the tractor's diagnostic display. Test the fender switch to ensure the PTO engages and disengages properly and that Code 157 does not return.