Case IH 111 – Transmission Control Unit (TCU): Engine Stall prevention by shifting the transmission to neutral

The controller has detected that the engine RPM is dropping too rapidly or is too low while under load, risking an engine stall. To protect the engine and driveline, it automatically commands the transmission to shift into neutral. This frequently triggers alongside other transmission codes due to a dead short in the transmission electrical circuit.

• STX Steiger
• Steiger Series
• Steiger 330
• Magnum
• Puma

1. 1

   Check the powershift (PS) transmission fuses in the cab (specifically fuse #39 on Steiger models). If the fuse blows when shifting into gear, there is a dead short.

2. 2

   Disconnect the park brake solenoid, replace the fuse, and try to shift into gear to isolate if the short is in the solenoid.

3. 3

   Pull the park brake relay entirely. If the fuse stops blowing, the short is in the wiring harness between the cab connector, the Bottom of Brake (BOB) switch, and the solenoid.

4. 4

   Inspect the driveline speed sensor wires under the tractor for damage or shorting against the chassis caused by field debris.

5. 5

   Verify engine health (fuel filters, air filters, and fuel pressure) to ensure the engine isn't actually losing power under load.

1. 1

   Locate the Short

   Use a multimeter to trace the wiring from the park brake relay to the Bottom of Brake (BOB) switch (normally closed), and down to the park brake solenoid.

2. 2

   Inspect Connectors

   Disconnect the cab-to-transmission harness connectors. Look for moisture, mud, or pushed-out pins. Clean with contact cleaner and apply dielectric grease.

3. 3

   Repair Wiring

   If the driveline speed sensor wiring or park brake solenoid wiring is chafed or torn by debris, cut out the damaged section. Solder in new wire and seal it with dual-wall adhesive heat shrink to make it weatherproof.

4. 4

   Replace Faulty Components

   If the wiring tests good but the park brake solenoid has high resistance or is internally shorted to ground, replace the solenoid.

5. 5

   Clear Codes and Test

   Replace any blown fuses. Start the tractor, clear the inactive fault codes from the display, and test drive the machine under load to ensure the transmission holds gear without defaulting to neutral.