New Holland TRANS 122 – Transmission Control Unit (TCU): High range clutch solenoid coil or its wiring shorted to power.

The transmission controller has detected unexpected positive voltage on the circuit responsible for controlling the high range clutch solenoid. When this circuit is shorted to power, the controller cannot properly modulate the clutch, which typically results in the system disabling the high range or the affected clutch pack to prevent mechanical damage.

• TG210
• TG230
• TG255
• TG285
• T7.175
• T7.190
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8 Series
• T9 Series

1. 1

   Test Solenoid Resistance (Internal Short Cause): Disconnect the electrical connector at the High Range Clutch Solenoid. Measure resistance across the coil pins. Expected: 8 to 11 Ohms. A reading near 0 Ohms indicates an internally shorted solenoid.

2. 2

   Test for Short to Power (Wiring Cause): If solenoid resistance is good, disconnect the CCU connectors. Turn ignition ON and measure voltage between the solenoid signal wire and chassis ground. 12V indicates the wiring harness has rubbed through and is shorting to power.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Access the Valve Block

   Locate the transmission control valve block on the side of the transmission housing where the clutch solenoids are mounted.

3. 3

   Address the Root Cause

   If the solenoid failed the resistance test: Remove the retaining bolt/nut securing the High Range Clutch Solenoid. Pull the faulty solenoid cartridge from the valve block. Lubricate the O-rings on the new solenoid with clean transmission fluid and install it. Torque the retaining hardware to OEM specifications. If the wiring failed the voltage test: Trace the wiring harness from the solenoid back to the CCU. Look for pinch points, melted insulation, or areas where the harness rubs against the chassis. Repair the damaged wire(s) using heat-shrink butt connectors and re-loom the harness.

4. 4

   Reassemble

   Reconnect the solenoid electrical connector and the CCU connectors. Reconnect the battery.

5. 5

   Clear Codes

   Turn the key ON and use the tractor's diagnostic menu or an electronic service tool to clear the TRANS 122 fault code.

6. 6

   Perform Calibration

   Perform a transmission clutch calibration procedure (often accessed by installing a diagnostic switch/tool and cycling to the 'H1' menu in the instrument cluster) so the controller can learn the fill times for the new valve.