Case IH 2577 – Transmission Controller: Wheel speed (transmission output speed) sensor #2 - short to 12V

The control module has detected an abnormally high voltage (a short to a 12-volt power source) on the circuit belonging to the second transmission output speed sensor. This disrupts the signal, often resulting in disabled shifting or limited transmission functionality.

• Optum
• Case IH Puma Series
• Case IH Magnum Series

1. 1

   Inspect the transmission output speed sensor #2 connector and the main transmission controller connectors for corrosion, bent pins, or moisture.

2. 2

   Connect the service tool or use the tractor's instrumentation controller to view the live input voltage/signal (a constant high voltage reading confirms the short).

3. 3

   Disconnect the sensor and test the wiring harness back to the UCM for a short to a 12V power source.

4. 4

   With the sensor disconnected, check the sender terminals for internal shorts to determine if the sensor itself has failed.

1. 1

   Power Down

   Turn off the tractor, engage the parking brake, and disconnect the battery to prevent electrical spikes during repair.

2. 2

   Locate the Sensor

   Locate transmission output speed sensor #2 on the side of the transmission extension assembly/housing.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a short to 12V in the harness (e.g., chafed wires touching a power wire), repair the damaged section of the wiring harness and secure it in a protective loom.

4. 4

   Replace the Sensor

   If the harness is intact and the sensor is internally shorted, remove the retaining bolt holding the speed sensor in the transmission housing. Pull the old sensor out, lubricate the O-ring on the new sensor, and install it.

5. 5

   Clear Codes and Test

   Reconnect the sensor and battery. Turn the key on and use the service tool or monitor to clear the 2577 error code.

6. 6

   Operational Test

   Drive the tractor to verify that the transmission output speed registers correctly on the monitor and that normal shifting operation has returned.