Case IH 2625 – ZTC: Transmission input shaft speed sensor (N_An) is open circuit or shorted to power

The controller is detecting an electrical anomaly—either a broken wire/disconnected sensor (open circuit) or a wire that is improperly touching a voltage source (shorted to power). Because of this, the controller cannot read the rotational speed of the transmission's input shaft, which is critical for calculating gear ratios and managing clutch engagement.

• Steiger T4B
• Case IH Puma CVX / CVT series
• Case IH Optum CVX series
• Case IH Maxxum CVX series
• Case IH Magnum series

1. 1

   Visually inspect the wiring harness routed between the ZF Transmission Controller (ZTC) and the N_An input speed sensor for chafed wires, breaks, or melted insulation

2. 2

   Disconnect the sensor and inspect the pins on both the sensor and the harness side for corrosion, bent pins, or moisture ingress

3. 3

   Using a multimeter, check the sensor's signal wire for continuity back to the ZTC to rule out an open circuit

4. 4

   Check the signal line for voltage when disconnected to test for a short circuit to a high source (+)

5. 5

   Test the internal resistance of the sensor itself to see if the internal coil has failed (open circuit)

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes to the ZTC.

2. 2

   Locate the Sensor

   Locate the N_An input shaft speed sensor on the transmission housing (often located near the front/input side of the transmission block).

3. 3

   Disconnect

   Unplug the electrical pigtail/harness connector from the sensor.

4. 4

   Remove

   Use a socket (typically 3/8" or metric equivalent) to remove the sensor's retaining bolt. Pull the sensor out of the transmission housing using a smooth, twisting motion.

5. 5

   Prep the Area

   Clean the mounting surface on the housing, ensuring no dirt or burrs fall into the transmission.

6. 6

   Install New Sensor

   Lubricate the O-ring on the new sensor with clean transmission fluid or an approved silicone lubricant. Fully insert the new sensor into the housing.

7. 7

   Secure

   Install the retaining bolt and torque to specification (generally 8–10 lb-ft or 11–13 N•m).

8. 8

   Reconnect

   Plug the transmission harness back into the sensor.

9. 9

   Clear Codes

   Reconnect the battery, connect a diagnostic tool to the tractor, and clear the stored 2625 fault code from the ZTC. Test drive to verify the transmission shifts smoothly and the code does not return.