Case IH PE1 – Transmission Control Unit (TCU): Transmission oil plausibility error (transmission oil temperature signal out of limits)

This code is triggered when the transmission controller receives an implausible temperature reading from the transmission oil temperature sensor. Specifically, the fault is logged under two conditions: 1. The transmission oil temperature signal reads greater than 115°C (239°F). 2. The transmission oil temperature AND the engine coolant temperature both read greater than 85°C (185°F) in a way that contradicts expected thermal mapping (implausible compared to actual fluid temperatures).

• MXM
• MXM Series
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• Puma Series
• Magnum Series
• TM Series
• TM115-TM165
• T8 Series

1. 1

   Verify that the transmission oil level is correct, as low fluid can cause actual overheating and trigger the 115°C threshold.

2. 2

   Inspect the wiring harness and connectors leading to the transmission oil temperature sensor for chafed wires causing a short to ground (low voltage) or a short to +V / open circuit (high voltage).

3. 3

   Perform a sensor plausibility test using a diagnostic tool or multimeter to compare the transmission oil temperature reading against the engine coolant temperature when the tractor is cold (both should read roughly ambient temperature).

1. 1

   Prep the Machine

   Park the tractor on a level surface, lower all equipment to the ground, place all shift levers in neutral, and block the front and rear wheels.

2. 2

   Locate the Sensor

   Locate the transmission oil temperature sensor on the transmission housing.

3. 3

   Test the Circuit

   Disconnect the sensor harness. Turn the key switch to the "ON" position and test the connector for the standard 5V reference signal.

4. 4

   Replace the Sensor

   If the wiring is intact and providing the correct reference voltage, the sensor itself is faulty. Unthread the old sensor (have a catch pan ready for minor fluid loss) and install the new OEM sensor.

5. 5

   Calibrate the Transmission

   According to the Case IH MXM/Puma service manuals, replacing a transmission sensor or potentiometer requires a transmission calibration. Start the engine, hold the High and Low range buttons until "CAL" appears on the transmission display, set engine speed to 1200 RPM, and follow the on-screen prompts to complete the "HA" mode calibration.