Case IH 146 – Transmission Controller (TCU): Regulated System Pressure Out Of Range High

The transmission controller continuously monitors the regulated hydraulic system pressure. If the pressure increases beyond a preset upper limit, this fault code is recorded. The two primary failure modes are a misadjusted/sticking transmission regulated pressure valve or a faulty pressure sensor/circuit.

• STX Steiger
• Steiger / STX 4WD Tractors
• STX275
• STX325
• STX375
• STX425
• STX500
• Magnum Series
• MX Magnum
• 7100 series
• 7110
• 7120
• 7140
• Magnum 225-380
• Puma Series
• Puma 130-240
• Maxxum Series
• Maxxum 110-150

1. 1

   Install a manual hydraulic test gauge into the transmission regulated pressure test port (typically located on the side of the transmission case near the shift accumulators or transmission control valve).

2. 2

   Start the tractor, warm up the hydraulic oil, and run the engine at the specified RPM (usually around 1100-1500 RPM depending on the model). Compare the manual gauge reading to the pressure reading displayed on the tractor's monitor.

3. 3

   If the manual gauge shows normal pressure (typically around 290–340 PSI depending on the specific model and gear) but the monitor reads excessively high, the sensor or its wiring is faulty.

4. 4

   If the manual gauge confirms the pressure is actually too high, the transmission regulated pressure valve is misadjusted or sticking.

5. 5

   If you suspect the sensor, inspect the wiring harness connecting to the transmission oil pressure sensor for shorts to power or ground before replacing the sensor.

1. 1

   Locate sensor

   Scenario A (Faulty Sensor): Locate the transmission regulated oil pressure sensor on the transmission control valve block.

2. 2

   Disconnect connector

   Disconnect the sealed multi-pin weather-pack connector.

3. 3

   Remove old sensor

   Unthread the old sensor from the port. Expect a small amount of hydraulic fluid loss.

4. 4

   Install new sensor

   Thread in the new OEM pressure transducer and tighten to factory torque specs.

5. 5

   Reconnect and test

   Reconnect the wiring harness, clear the fault codes via the tractor's diagnostic menu, and test drive to verify the code does not return.

6. 6

   Locate priority valve

   Scenario B (Actual High Pressure): Locate the transmission priority valve / regulated pressure valve assembly.

7. 7

   Inspect and clean valve

   Remove the priority valve and inspect the spool for scoring, debris, or sticking. Clean the assembly thoroughly.

8. 8

   Adjust regulated pressure

   Adjust the regulated pressure. Depending on the tractor model, this is done either by adjusting a set screw or by removing shims from the regulator valve spring pack to lower the pressure.

9. 9

   Reinstall and re-test

   Reinstall the valve, attach your manual gauge, and re-test the pressure in all gears (including forward and reverse) to ensure the pressure remains within the safe OEM specification.