Case IH 4373 – UCM (Universal Control Module): Reverse Pump Control Valves (Directional) - Solenoid Left (B) Supply STP (Short to Power)

The controller has detected a Short to Power (STP) on the supply circuit for the left directional reverse pump control valve solenoid. (Note: The swashplate angle sensor out of range low condition is also covered in the diagnostic steps, though it corresponds to codes 473x/474x).

• Steiger T4B
• Case IH Steiger Quadtrac tractors (e.g., 715, 785)
• Case TR270 compact track loaders

1. 1

   Locate the hydrostatic pump and visually inspect the swashplate angle sensors (mounted on the bottom of the pump, often protected by steel covers) and the directional control valve solenoids.

2. 2

   Check the specific wiring harnesses (e.g., X-93 for the right pump, X-94 for the left pump) for chafing, melted insulation, or corrosion.

3. 3

   Use a multimeter to verify the 5V reference supply to the sensor; a loss of the 5V supply will cause the sensor to read out of range low.

4. 4

   Test the specific pins (Pin A or Pin B) for continuity to ground (to confirm an STG/OC condition for the sensor) or for a short to a voltage source (to confirm the STP condition for code 4373).

1. 1

   Preparation

   Turn off the engine, lower any lift arms (or secure them with an approved support device), and disconnect the battery to prevent accidental shorting.

2. 2

   Clean the Area

   Thoroughly clean the forward solenoid, reverse solenoid, and swashplate angle sensor area on the hydrostatic pump to prevent dirt from entering the hydraulic system.

3. 3

   Remove the Component

   Remove the steel protective covers over the sensors, disconnect the 4-pin DEUTSCH connector from the sensor or solenoid, and remove the mounting bolts securing the faulty swashplate angle sensor or reverse pump control valve.

4. 4

   Install the New Part

   Insert the replacement sensor/solenoid and tighten the mounting bolts to the OEM specification (e.g., 27.4 in.-lb / 3.1 N·m).

5. 5

   Reassembly

   Reinstall the steel protective covers, ensuring the connectors are facing the correct direction, and reconnect the wiring harness.

6. 6

   Calibration

   Reconnect the battery, connect the Electronic Service Tool (EST) to the machine's diagnostic port to clear the fault codes, and navigate the machine's InfoCenter or EST to check and calibrate the swashplate position variance.