Case IH 2633 – ZTC: ZTC - Hydrostatic unit speed sensor not plausible, number of teeth N_Hyd1 is less than N_Hyd2

This code indicates a signal discrepancy between the two speed sensors (N_Hyd1 and N_Hyd2) monitoring the hydrostatic unit inside a continuously variable transmission (CVT). The controller is reading the pulse count and has detected that the count from sensor N_Hyd1 is implausibly lower than the count from sensor N_Hyd2, usually pointing to a failing sensor, a wiring issue, or debris interfering with the sensor's magnetic pickup.

• Steiger T4B
• Puma CVX
• Maxxum CVX
• Optum
• Magnum

1. 1

   Access the tractor's 'Test - Transmission' menu via the cab display and navigate to the 'Internal TCU 2' screen to compare live readings of N_Hyd1 and N_Hyd2 while moving.

2. 2

   Check the wiring harness leading to the N_Hyd1 and N_Hyd2 sensors on the transmission housing for a short circuit to minus, short circuit to plus, or an open circuit.

3. 3

   Remove the N_Hyd1 sensor and inspect the magnetic tip for metal shavings or debris that could cause it to miss gear teeth.

1. 1

   Safety Prep

   Park the machine on a level surface, engage the park brake, and allow the transmission oil to cool down to prevent burns.

2. 2

   Disconnect Power

   Disconnect the battery terminals (negative terminal first) to prevent electrical spikes to the ZTC module.

3. 3

   Locate the Sensor

   Locate the hydrostatic unit speed sensors on the side of the ZF transmission housing.

4. 4

   Removal

   Unplug the electrical connector from the N_Hyd1 sensor. Remove the retaining screw holding the sensor in place.

5. 5

   Installation

   Lubricate the O-ring on the new sensor with clean transmission oil. Insert the new sensor into the transmission housing.

6. 6

   Torque

   Tighten the hydrostatic unit speed sensor mounting screw. (Standard torque for CVT hydrostatic speed sensors is typically 9.5 N·m / 7.0 lb-ft).

7. 7

   Reassembly

   Reconnect the wiring harness and the battery terminals.

8. 8

   Calibration/Clear Codes

   Turn the key on, clear the inactive 2633 fault code from the ZTC module, and test drive the tractor to ensure the N_Hyd1 and N_Hyd2 signals are now synchronized.