Massey Ferguson T4145 – TRANS: Transmission Output Speed Sensor Issue DYNA VT / Bevel gear theoretical speed sensor Signal error

The transmission control unit is detecting a signal error or miscalculation from the transmission output speed sensor (specifically the bevel gear theoretical speed sensor). When this code is triggered, the tractor will automatically enter 'gearbox protection mode' (limp mode) to prevent mechanical damage.

• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 7615
• 7620
• 7616
• 7618
• 7619
• 7626
• 7624

1. 1

   Verify the transmission oil level and quality, as low or highly polluted hydraulic/transmission oil can cause erratic sensor readings.

2. 2

   Inspect the wiring harness leading to the transmission speed sensors for chafing, shorts to ground, or loose connections.

3. 3

   Test the bevel gear speed sensor for proper resistance and signal output.

1. 1

   Prepare machine

   Safely park the tractor, lower all implements, and disconnect the battery.

2. 2

   Locate sensors

   Locate the transmission output speed sensors on the DYNA VT transmission housing. (Note: The DYNA VT transmission utilizes two of these sensors for calculation).

3. 3

   Disconnect wiring

   Disconnect the electrical connector from the faulty speed sensor.

4. 4

   Remove sensor

   Unbolt and remove the sensor from the transmission housing. Be prepared to catch a small amount of transmission fluid.

5. 5

   Install new sensor

   Install the new sensor with a new O-ring (if applicable) to prevent leaks.

6. 6

   Reconnect wiring

   Reconnect the wiring harness.

7. 7

   Clear codes and test

   Clear the fault codes using a diagnostic tool and perform a test drive to ensure the transmission shifts out of protection mode. Note: OEM documentation heavily advises that if the tractor enters gearbox protection mode due to this sensor fault, the operator should 'Contact your dealer' for advanced transmission calibration.