Fendt 4.1.73 – Transmission Control Module: Signal fault or signal failure from the B033 Discharge oil temperature sensor

The control module has lost the electrical signal from the sensor that monitors the transmission discharge oil temperature. As a consequence, there is no further display or monitoring of the transmission temperature, which can lead to severe transmission damage if the tractor overheats without the operator knowing.

• 409 Vario
• 410 Vario
• 411 Vario
• 412 Vario
• 711 Vario
• 712 Vario
• 714 Vario
• 715 Vario
• 716 Vario
• 717 Vario
• 718 Vario
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario
• Farmer 400 Vario series
• Favorit 700 Vario series
• Favorit 900 Vario series
• 800 Vario series

1. 1

   Visually inspect the B033 sensor on the transmission housing and its electrical connector for corrosion, moisture, dirt, or backed-out pins.

2. 2

   Trace and check the wiring harness from the B033 sensor back to the Transmission Control Module for chafed wires, open circuits, or shorts to ground/power.

3. 3

   Perform a resistance test on the B033 temperature sensor using a multimeter; an open circuit (infinite resistance) or a dead short indicates the sensor has failed internally.

4. 4

   Check the transmission oil level and filter condition to ensure no mechanical overheating event caused the sensor to melt or fail.

1. 1

   Park and secure tractor

   Safely park the tractor on level ground, turn off the engine, remove the key, and engage the parking brake.

2. 2

   Locate sensor

   Locate the B033 Discharge oil temperature sensor on the transmission block.

3. 3

   Disconnect harness

   Disconnect the electrical wiring harness from the sensor.

4. 4

   Prepare for oil leak

   Place a clean catch pan underneath the sensor area to catch any transmission oil that may leak out during removal.

5. 5

   Remove sensor

   Using the appropriate wrench or deep socket, unscrew and remove the faulty B033 sensor.

6. 6

   Lubricate new sensor

   Lubricate the O-ring/seal on the new sensor with a small amount of clean transmission fluid.

7. 7

   Install new sensor

   Thread the new sensor into the transmission housing by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

8. 8

   Reconnect harness

   Reconnect the electrical harness, ensuring the connector clicks securely into place.

9. 9

   Top up fluid

   Top up the transmission fluid if a significant amount was lost during the swap.

10. 10

    Clear fault code

    Connect a diagnostic tool (such as FENDIAS) to the tractor and clear the 4.1.73 fault code.

11. 11

    Verify repair

    Start the tractor and verify that the transmission temperature is reading correctly on the dash/Vario terminal and that the code does not return.