New Holland TRANS 105 – Transmission Control Module (TCM): C1-2 clutch solenoid or its wiring failed open or shorted to ground.

This indicates an electrical failure in the circuit controlling the C1-2 transmission clutch solenoid. The system has detected that the circuit is either broken (open) or the wiring/solenoid coil has shorted directly to the chassis ground, preventing the solenoid from actuating the clutch pack properly.

• TG210
• TG230
• TG255
• TG285
• T8010
• T8020
• T8030
• T8040
• T9020
• T4 Series
• T5 Series
• T6 Series
• T7 Series

1. 1

   Inspect the wiring harness and C1-2 solenoid connector for chafed wires, melted insulation, pinched lines, water ingress, corrosion, or loose pins.

2. 2

   Perform a solenoid resistance test (Ohm test) across the coil pins. An infinite reading indicates an internal open circuit, while 0 ohms indicates a short. Check for continuity to ground (there should be none).

3. 3

   Perform a harness continuity test between the TCM and the solenoid to ensure wires are not broken or shorted to the tractor frame.

4. 4

   Perform a swap test by exchanging the C1-2 solenoid with an adjacent identical solenoid (e.g., C3-4). Clear codes and operate the tractor to see if the fault code follows the solenoid.

5. 5

   Verify transmission/hydraulic oil level and condition. Burnt oil or heavy debris can indicate the electrical failure caused the clutch pack to slip.

1. 1

   Preparation

   Park the tractor on a level surface, engage the parking brake, lower all implements, and turn off the engine. Disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Locate the Valve Block

   Locate the transmission control valve block (usually mounted on the side or top of the transmission housing, depending on the specific tractor model).

3. 3

   Clean the Area

   Thoroughly clean the area around the C1-2 solenoid with brake cleaner and compressed air to prevent dirt from entering the transmission hydraulic circuits.

4. 4

   Remove the Solenoid

   Disconnect the electrical plug. Remove the retaining bolts or snap ring holding the C1-2 solenoid in the valve block. Pull the solenoid straight out. Have a catch pan ready, as a small amount of hydraulic fluid will leak out.

5. 5

   Install the New Solenoid

   Lubricate the O-rings on the new solenoid with clean OEM-specified transmission fluid. Carefully insert the new solenoid into the valve block, ensuring the O-rings do not pinch or roll.

6. 6

   Secure and Reconnect

   Install and torque the retaining bolts to factory specifications. Reconnect the electrical harness, ensuring the locking tab clicks into place.

7. 7

   Clear Codes and Calibrate

   Reconnect the battery. Use a diagnostic scan tool or the tractor's onboard H-routine diagnostic menu to clear the TRANS 105 fault code.

8. 8

   Transmission Calibration

   You must perform a transmission clutch calibration procedure (often requiring the transmission fluid to be at a specific operating temperature, usually around 45-50°C) so the TCM can learn the engagement characteristics of the new solenoid.