Case IH 105 – Transmission Controller (TRANS / TCU): C1-2 clutch solenoid or its wiring has failed open or shorted to ground

The transmission controller monitors the electrical circuit for the C1-2 clutch solenoid (which controls hydraulic pressure to the C1/C2 clutch packs for specific gear ranges). If the controller detects zero current flow (an open circuit) or excessive current draw routing directly to the chassis ground (a short to ground) when the driver circuit is energized, it logs this code. This prevents the transmission from shifting into the gears that rely on the C1-2 clutch pack, often resulting in a loss of specific gears or a complete halt in movement.

• MX Magnum
• STX Steiger
• Magnum 235–340 (Series 4)
• MX210
• TG Series
• Puma Series
• Steiger Series (Powershift models)
• Farmall / Maxxum / JXU Series
• JXU105
• MXU135

1. 1

   Visual Inspection: Inspect the transmission control valve block (usually located on the side of the transmission housing) and the wiring harness leading to the C1-2 solenoid for chafing, melted insulation, or pinched wires.

2. 2

   Connector Check: Disconnect the C1-2 solenoid connector. Check for corrosion, moisture, or pushed-out pins.

3. 3

   Coil Resistance Test: Using a multimeter, measure the resistance across the pins of the C1-2 solenoid coil. If the multimeter reads OL (infinite resistance), the coil has failed open. If it reads near 0 ohms, the coil is internally shorted. If it is temperature-sensitive, the coil may be starting to fail and will test out of spec only when hot.

4. 4

   Harness Continuity & Ground Test: Disconnect the harness at the Transmission Controller and at the solenoid. Test the signal wire for continuity from end to end (to rule out an open wire). Test the signal wire for continuity to the chassis ground. If there is continuity to ground while both ends are unplugged, the wiring harness is shorted to ground and must be repaired.

1. 1

   Prep the Machine

   Park the tractor on a level surface, engage the parking brake, turn off the engine, and disconnect the battery to prevent electrical spikes.

2. 2

   Relieve Pressure

   Relieve any residual hydraulic pressure in the transmission system according to the operator's manual.

3. 3

   Locate and Remove

   Locate the C1-2 PMV (Proportional Magnetic Valve) solenoid on the transmission valve body. Disconnect its electrical connector.

4. 4

   Unbolt the Solenoid

   Remove the retaining bolts holding the solenoid to the valve body. Carefully pull the solenoid out, ensuring no dirt or debris falls into the hydraulic valve body.

5. 5

   Clean and Install

   Clean the mounting surface on the valve body. Lubricate the O-rings on the new solenoid with clean hydraulic transmission fluid. Insert the new solenoid and torque the retaining bolts to OEM specifications.

6. 6

   Reconnect

   Plug the electrical connector back in, ensuring the weather seal is intact and the latch clicks.

7. 7

   Calibrate

   Reconnect the battery, clear the TRANS 105 fault code via the diagnostic menu, and perform a mandatory transmission clutch calibration procedure so the controller can learn the fill times and threshold pressures of the new solenoid.