Case IH 161-08 - DEC – Transmission Control Module (TCM) or Transmission Electronic Control Unit (TECU): Abnormal Frequency or invalid signal from the Transmission Input Shaft Speed Sensor

The transmission control module detects that the input shaft speed signal is out of its normal operating frequency, erratic, or implausible when compared to the engine speed or output shaft speed. This can cause erratic shifting, failure to shift, or a complete loss of drive.

• MAGNUM AFS Connect
• Steiger series
• Quadtrac series
• 470
• 535 Quadtrac
• Magnum series
• MX285
• Maxxum series
• MX150
• MX170
• Puma series

1. 1

   Turn the disconnect switch to the OFF position. Inspect all harness connections related to the input shaft speed sensor. Ensure connectors are fully seated, clean, tight, and free of mud or moisture.

2. 2

   Disconnect the harness from the sensor and measure the resistance of the sensor itself (a good sensor typically measures around 3,000 ohms).

3. 3

   Measure the resistance across the sensor circuit pins at the machine harness connectors for the ECU (should be less than 5.0 ohms). High or infinite resistance indicates an open circuit in the harness.

4. 4

   Verify that the transmission is not slipping excessively, as mechanical clutch slip can trigger speed sensor plausibility faults.

1. 1

   Power Down

   Turn the key and the main battery disconnect switch to the OFF position.

2. 2

   Locate the Sensor

   Locate the transmission input shaft speed sensor. On many Case IH models, it is accessible externally on the side or top of the transmission housing.

3. 3

   Remove the Sensor

   Disconnect the machine harness connector from the sensor. Remove the retaining bolt(s) and carefully pull the sensor out of the transmission housing.

4. 4

   Install the New Sensor

   Lubricate the O-ring on the new sensor with clean transmission fluid. Insert the sensor into the housing and tighten the retaining bolt to the OEM specified torque.

5. 5

   Reconnect Wiring

   Reconnect the electrical harness, ensuring the locking clip is fully fastened.

6. 6

   Clear Fault Codes

   Power the tractor on. Note that on some Case IH models, inactive faults cannot be cleared simply by holding the INCR/DECR keys on the display; you may need to use the Case IH Electronic Service Tool (EST) laptop software to clear the codes from the memory and verify the repair.