Case IH 2049 (191.04) - DEC – Transmission Controller (TCU) / DEC (Drive Electronic Controller) / CCM (Central Control Module): Wheel speed (transmission output speed) sensor – short to ground or open circuit

The controller has detected an electrical fault in the transmission output speed sensor circuit. The system is either seeing a broken connection/wire (open circuit) or a wire that is improperly making contact with the tractor's chassis ground (short to ground), which prevents the sensor from accurately reading the vehicle's ground speed.

• MAXXUM T4E
• VESTRUM CVX
• Case IH Puma Series (165, 170, 180, 185, 195, 200, 210, 215, 225, 230 CVX)
• Case IH Maxxum Series (MXM 120, 130, 140, 155, 175, 190)
• Case IH Magnum Series (180, 235-340 Series 4)

1. 1

   Connect the electronic service tool, navigate to the monitor screen, and select 'inst trans output speed' to verify if any RPM signal is being generated.

2. 2

   Disconnect the sensor's electrical connectors (C026/C027 or X555) and verify they are fully seated. Inspect terminals and wires for pushed-back pins, corrosion, or damaged insulation.

3. 3

   Measure the resistance between the sensor connector cavity and the chassis ground. There should be infinite resistance (no continuity). If continuity exists, trace and repair the short to ground in the harness.

4. 4

   If wiring tests fine but the fault remains, suspect a faulty sensor or a physical fault with the internal speed sensor inductive ring inside the transmission.

1. 1

   Locate the Sensor

   The transmission output speed sensor is typically located on the transmission case or the rear axle housing.

2. 2

   Clean the Area

   Thoroughly clean the area around the sensor to prevent dirt or debris from falling into the transmission housing.

3. 3

   Disconnect Wiring

   Unplug the electrical wiring harness from the sensor.

4. 4

   Remove the Sensor

   Remove the retaining bolt/nut securing the sensor to the housing and carefully pull the old sensor out.

5. 5

   Prep the New Sensor

   Lubricate the new O-ring/seal (e.g., 1.4mm ID seal) with clean transmission fluid.

6. 6

   Install

   Insert the new sensor into the housing, install the retaining hardware, and torque to specification.

7. 7

   Reconnect and Clear

   Reconnect the electrical harness. Turn on the tractor, clear the stored fault codes using the diagnostic H-Menu or service tool, and test drive the tractor to ensure the transmission output speed registers correctly and the code does not return.