Massey Ferguson 04.X.85 – Transmission Control Unit (TCU): Issue With Speed Sensor Values (TRANS / TRANS1)

The transmission control system is receiving erratic, out-of-range, or missing signals from the speed sensor mounted on the transmission housing.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4700 Series
• 5600 Series
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5700 SL Series
• 6600 Series
• 6700 Series
• 7600 Series
• 7700 Series
• 8600 Series

1. 1

   Connect the tractor to the Wintest diagnostic software. Open the gearbox tab and look at the range window to monitor the live status of the speed/range sensors.

2. 2

   Perform an in-situ multimeter voltage test: Connect a diagnostic harness (OEM tool X899980246204) between the sensor and the tractor's wiring harness. Connect a multimeter to pins 1 and 2. Start the engine and engage the appropriate range. The voltage should read approximately 14V. Shift to another range, and the voltage should drop to 0V.

3. 3

   Perform a manual bench test: If the transmission is not shifting, remove the sensor. Connect it to the diagnostic harness and switch the ignition on. The multimeter should read 0V at rest, and jump to 14V when you manually press the ball/tip of the sensor.

4. 4

   Check the sensor's wiring harness and connectors for corrosion, moisture ingress, or physical damage, which frequently cause false sensor codes.

1. 1

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

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

2. 2

   Locate the transmission-mounted speed sensor on the gearbox housing.

   Locate the transmission-mounted speed sensor on the gearbox housing.

3. 3

   Clean the area around the sensor thoroughly to prevent dirt from entering the transmission.

   Clean the area around the sensor thoroughly to prevent dirt from entering the transmission.

4. 4

   Partially drain the transmission fluid if the sensor is located below the fluid fill line.

   Partially drain the transmission fluid if the sensor is located below the fluid fill line.

5. 5

   Disconnect the electrical connector from the faulty speed sensor.

   Disconnect the electrical connector from the faulty speed sensor.

6. 6

   Unbolt and carefully pull the sensor out of the transmission housing.

   Unbolt and carefully pull the sensor out of the transmission housing.

7. 7

   Lubricate the O-ring on the new sensor with clean transmission fluid.

   Lubricate the O-ring on the new sensor with clean transmission fluid.

8. 8

   Insert the new sensor into the housing and tighten the retaining bolt to the OEM torque specification.

   Insert the new sensor into the housing and tighten the retaining bolt to the OEM torque specification.

9. 9

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

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

10. 10

    Refill the transmission fluid to the correct level if any was drained.

    Refill the transmission fluid to the correct level if any was drained.

11. 11

    Reconnect the battery, turn on the ignition, and use a diagnostic tool to clear the 04.X.85 fault code.

    Reconnect the battery, turn on the ignition, and use a diagnostic tool to clear the 04.X.85 fault code.

12. 12

    Test drive the tractor through all ranges to ensure smooth shifting and verify the code does not return.

    Test drive the tractor through all ranges to ensure smooth shifting and verify the code does not return.