Fendt 4.1.89 – Transmission Control System (A002 ECU or A050 ECU): B009 - Discharge temperature sensor

Plausibility error, transmission temperature. This indicates that the sensor is supplying an implausible temperature reading, which usually points to a faulty sensor or a wiring issue.

• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Fendt 300 Vario (COM III / S4)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III / S4)
• Fendt 800 Vario (COM III / S4)
• Fendt 900 Vario (COM III / S4)

1. 1

   Terminal Live Data Check: Use the Variotronic Ti terminal (Diagnostics menu A008) to check the live reading of the B009 discharge temperature sensor. If the reading is erratic, pegged at an extreme, or drops out, the sensor or wiring is failing.

2. 2

   Wiring & Connector Inspection: Inspect the wiring harness and the connector leading to the B009 sensor (located on the transmission high-pressure circuit) for short circuits, open circuits, corrosion, or physical damage.

3. 3

   Fluid Condition: Pull the transmission dipstick and check the oil. If the oil smells burnt or acrid, the transmission has genuinely overheated, which may have damaged the sensor or indicates a severe mechanical/hydraulic issue.

1. 1

   Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Locate the B009 discharge temperature sensor on the transmission housing.

   Refer to the transmission high-pressure circuit block.

3. 3

   Disconnect the electrical harness from the B009 sensor and clean the surrounding area.

   This prevents dirt from entering the transmission housing.

4. 4

   Test the wiring harness for continuity back to the transmission ECU.

   If the wiring is damaged, repair the harness. If the wiring is intact, the sensor itself is faulty.

5. 5

   Unscrew and remove the faulty B009 temperature sensor.

   Note: Be prepared for minor fluid loss; have a catch pan ready.

6. 6

   Install the new OEM temperature sensor and tighten to the manufacturer's specified torque.

7. 7

   Reconnect the electrical harness.

8. 8

   Check the transmission oil level.

   Top up with approved fluid (Fendt Extra Trans 10W-40 or STOU 15W-40) if necessary.

9. 9

   Turn on the ignition and use the FENDIAS diagnostic tool or the Variotronic Ti terminal to clear the stored 4.1.89 fault code.

10. 10

    Test drive the tractor while monitoring the B009 live data on the terminal.

    Ensure the temperature rises plausibly and the fault code does not return.