Case IH 1049 – Transmission Control Unit (TCU) or Vehicle/Chassis Controller: Open circuit in the wheel speed sensor

The controller is not detecting a complete electrical path to the wheel speed sensor, which prevents the system from reading the tractor's ground speed.

• Puma/Mid Range Magnum
• Maxxum
• MAXXUM T4E
• VESTRUM CVX
• Farmall
• Case IH Puma and SWB Puma series
• Case IH Magnum and Maxxum series (e.g., MX255)
• Case IH CX Series (CX50, CX60, CX70, CX80, CX90, CX100)
• Case IH Crawler Dozers (450H, 550H, 650H, 700H, 750C, 850C)

1. 1

   Visually inspect the wheel speed sensor and wiring harness pigtail for severed wires, chafing against the chassis, or a disconnected plug.

2. 2

   Unplug the sensor and check the connector pins for heavy corrosion, moisture ingress, or pushed-out terminals that would break the circuit.

3. 3

   Use a multimeter to measure the internal resistance of the sensor across its pins. An infinite reading (OL) confirms the sensor's internal coil has failed open and the sensor must be replaced.

4. 4

   If the sensor tests good, check the wiring harness for continuity back to the transmission or chassis controller to rule out a broken wire in the main loom.

1. 1

   Locate the Sensor

   The wheel speed sensor is typically mounted on the side of the transmission housing, the final drive, or the axle housing (location varies by exact model).

2. 2

   Clean the Area

   Thoroughly clean the area around the sensor base to prevent dirt or debris from falling into the transmission/axle housing when the sensor is removed.

3. 3

   Disconnect

   Unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Remove the retaining bolt securing the sensor bracket. Carefully twist and pull the sensor out of its bore.

5. 5

   Install the New Sensor

   Lightly lubricate the O-ring on the new sensor with clean hydraulic/transmission oil. Push it squarely into the bore until seated.

6. 6

   Secure and Reconnect

   Install and tighten the retaining bolt. Reconnect the electrical harness, ensuring the locking tab clicks into place.

7. 7

   Clear Codes and Test

   Clear the fault codes via the cab monitor or by cycling the battery power. Test drive the tractor to ensure ground speed is now registering on the A-post or dash display and that the transmission shifts normally.