Case IH 191-08 - DEC – Transmission Electronic Control Module (Transmission ECM / TCU): Transmission Output Speed Sensor Abnormal Frequency, Pulse Width, or Period

The control module is either receiving no signal from the output shaft speed sensor(s), or the signal being received is erratic, intermittent, or mathematically invalid compared to the expected parameters.

• MAGNUM AFS Connect
• Magnum 180
• Magnum 210
• Magnum 235
• Magnum 245
• Magnum 255
• Magnum 275
• Magnum 340
• Maxxum MXM 120
• Maxxum MXM 130
• Maxxum MXM 140
• Maxxum MXM 155
• Maxxum MXM 175
• Maxxum MXM 190
• Puma Series

1. 1

   Connect the Case IH Electronic Service Tool (EST) and observe if the sensor outputs a valid RPM reading while the machine is moving

2. 2

   Inspect the transmission output speed sensor wiring harness and connectors (specifically 4-way connectors like X555 or X551) for corrosion, backed-out pins, or wire chafing

3. 3

   Compare signals from both output speed sensors (TOS #1 and TOS #2) if equipped; if both fail, check for a wiring short to ground or a 5-Volt reference failure

4. 4

   Ensure the sensor is seated correctly, as a loose sensor or excessive gap between the sensor tip and the transmission output gear will cause an abnormal frequency reading

1. 1

   Park the tractor on a flat, level surface, engage the parking brake, and turn off the engine.

   Ensure the machine is safely secured before beginning work.

2. 2

   Locate the Transmission Output Speed Sensor on the transmission housing.

   Typically located on the rear axle housing or main gearbox drive section.

3. 3

   Clean the area around the sensor.

   This prevents dirt from entering the transmission during removal.

4. 4

   Depress the locking tab and disconnect the electrical connector from the sensor.

   Carefully remove the harness connection.

5. 5

   Remove the retaining bolt holding the sensor to the transmission housing.

   Unbolt the sensor from its mounting point.

6. 6

   Carefully pull the sensor straight out.

   Note: Have a shop rag ready, as a small amount of transmission/hydraulic fluid may seep out.

7. 7

   Lubricate the O-ring/seal on the new sensor.

   Use clean Case IH Hy-Tran fluid for lubrication.

8. 8

   Insert the new sensor into the housing.

   Ensure it seats fully, and tighten the retaining bolt to OEM torque specs.

9. 9

   Reconnect the electrical harness.

   Plug the connector back into the new sensor.

10. 10

    Clear the fault codes using the diagnostic service tool and perform a test drive.

    Verify the transmission shifts correctly and the code does not return.