Massey Ferguson 04.X.91 – Transmission Control Unit (TCU): Issue With Speed Sensor Values (TRANS1 / TRANS)

The controller is receiving erratic, implausible, or missing electrical signals from the transmission speed sensor (which monitors ground speed, intermediate speed, or input shaft speed). This can cause rough shifting, poor fuel economy, or a complete refusal to shift ranges.

• 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
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 6400 Series
• 6600 Series
• 7600 Series
• 8600 Series
• 8700 Series

1. 1

   Check Sensor Resistance: Turn the ignition off and disconnect the sensor. Using a multimeter, check the resistance across the sensor pins at room temperature. A healthy sensor typically reads 450 ohms (± 20 ohms) or 540 ohms depending on the specific part revision.

2. 2

   Check Sensor Adjustment (Air Gap): The sensor may simply be located too close to or too far away from the internal gear. Adjusting the depth of the sensor can often resolve the fault.

3. 3

   Inspect Wiring: Check the wiring harness and the connector pins for corrosion, moisture, or damage. Ensure the multimeter pins make good contact during testing.

4. 4

   Software Diagnostics: Use Massey Ferguson's Wintest diagnostic software to monitor the live active and requested speed values to confirm if the sensor is dropping the signal under load.

1. 1

   Locate the Sensor

   The transmission/ground speed sensor is typically threaded into the side of the transmission housing or near the hydraulic pump underneath the tractor.

2. 2

   Disconnect Battery & Wiring

   Disconnect the tractor's battery to prevent short circuits, then unplug the electrical connector from the speed sensor.

3. 3

   Remove the Sensor

   Unscrew the faulty sensor from the transmission housing. Have a catch pan ready, as a small amount of transmission oil may weep from the port.

4. 4

   Install the New Sensor

   Thread the new sensor into the housing. If it is an adjustable depth sensor, carefully set the clearance to the internal gear as per the specific model's service manual to prevent the gear from striking the sensor tip.

5. 5

   Reconnect and Clear Codes

   Reconnect the wiring harness. Power up the tractor and use the diagnostic interface (or Wintest software) to clear the 04.X.91 fault code.