Case IH 6912-04 - DEC – Transmission Control Module (TCU): Transmission hydro motor speed sensor electrical circuit fault voltage below normal

A low voltage condition in the electrical circuit of the transmission's hydro motor speed sensor, indicating the controller is receiving a signal voltage that has dropped below the acceptable threshold.

• MAGNUM AFS Connect
• Case IH Magnum series (e.g., Magnum 340)

1. 1

   Check system voltage to ensure battery voltage has not dropped below 11.5 volts, verifying battery health and alternator output.

2. 2

   Inspect plug connections and cables leading to the hydro motor speed sensor for corrosion, backed-out pins, or chafing that could cause a short to ground.

3. 3

   Verify the sensor setting and ensure it is transmitting a valid frequency/voltage signal to the controller.

1. 1

   Power Cycle

   Restart the vehicle to see if the error is an active or stored/pending fault.

2. 2

   Harness Repair

   If the wiring inspection reveals a short to ground or broken wire (causing the low voltage reading), repair the affected section of the harness or replace the connector (e.g., 2-pole female connector).

3. 3

   Sensor Replacement

   If the circuit tests good (proper reference voltage and ground from the module) but the fault persists, the hydro motor speed sensor itself has failed internally and must be replaced.