Case IH 122 – TRANS or UCM: High range clutch solenoid coil or its wiring shorted to power.

The transmission controller is detecting an abnormally high voltage on the circuit responsible for the high range clutch solenoid, indicating that the electrical current is bypassing its normal path and shorting directly to a power source. This prevents the transmission from properly engaging or modulating the high range clutch.

• MX Magnum
• MX Magnum Series
• TG Series
• Puma Series
• MXM Series
• Steiger Series

1. 1

   Test Solenoid Resistance: Disconnect the electrical connector at the high range clutch solenoid and measure resistance across the pins. It should read between 8 to 11 Ohms. An out-of-range reading indicates internal failure.

2. 2

   Test for Short to Positive Voltage (Wiring Harness): If the solenoid tests okay, disconnect the main transmission harness from the UCM/TCU. Turn the ignition ON (engine off) and measure voltage between the high range clutch signal wire and chassis ground. A 12V reading indicates the wiring harness has rubbed through and is shorting to a live power wire.

1. 1

   Safety First

   Turn off the tractor, apply the parking brake, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Locate the Solenoid

   Locate the transmission control valve block (usually mounted on the side or top of the transmission housing). Identify the specific solenoid for the "High Range" clutch (refer to your specific model's hydraulic schematic, as placement varies).

3. 3

   Wiring Repair

   If the diagnostic test revealed a short to power, trace the wiring harness from the transmission back to the cab/TCU. Look for pinch points, melted loom, or areas where the harness rubs against the chassis. Splice and repair the damaged wires using weather-sealed connectors.

4. 4

   Solenoid Replacement

   Clean the area around the solenoid to prevent dirt from entering the transmission valve body. Remove the retaining nut or bolt holding the solenoid coil to the valve stem. Slide the faulty coil off the valve cartridge (or remove the entire cartridge valve if it is a single-piece unit). Lubricate the O-rings on the new solenoid with clean transmission/hydraulic fluid. Install the new solenoid and torque the retaining nut to OEM specifications (do not overtighten, or you may warp the valve).

5. 5

   Reassembly & Calibration

   Reconnect the electrical harness and battery. Start the tractor and clear the fault codes. Crucial step: You must perform a transmission clutch calibration procedure via the tractor's display monitor so the TCU can learn the engagement profile of the new solenoid.