Case IH P35 – Electronic Management Unit (EMU): Fender Mounted Rear PTO Switch Input Short To +12v Or Short Across Fender Switch Wires

The controller is detecting an improper voltage signal from the external Power Take-Off (PTO) switch located on the rear fender. The system sees either a direct short to a 12-volt power source or a short circuit across the two wires leading to the switch, which prevents the safe operation of the rear PTO.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Puma Series
• Maxxum Series
• MX / TG Series
• CVX 170
• Farmall 95U
• Farmall 105U
• Farmall 115U

1. 1

   Inspect the rear fender PTO switch for physical damage, water ingress, or packed debris that could cause an internal short.

2. 2

   Disconnect the wiring harness from the fender switch and use a digital multimeter to check continuity, verifying the switch is not internally shorted across its terminals.

3. 3

   Trace the wiring harness from the fender switch back to the EMU (specifically checking the circuit leading to the C105 touch panel connector) for wires that have rubbed bare against the chassis or melted together.

1. 1

   Turn the tractor key to the OFF position to ensure the circuit is unpowered.

2. 2

   Disconnect the wiring harness connector at the rear fender PTO switch.

3. 3

   Repair or replace the shorted component based on diagnostic results.

   If the switch is internally shorted: Remove the retaining nut/clips holding the switch to the fender housing, pull the old switch out, and install a replacement switch. If the wiring is shorted: Locate the chafed or damaged section of the wiring harness. Splice and solder the broken wires, sealing them with heat-shrink tubing, or replace the affected harness section entirely.

4. 4

   Reconnect the wiring harness to the fender switch.

5. 5

   Cycle the ignition key OFF, then ON to reset the EMU and ensure the error code is eliminated.

6. 6

   Test the PTO engagement safely to confirm the repair.