Massey Ferguson 04.01.85 – TRANS1: Issue With Speed Sensor Values (TRANS1)

The transmission controller is detecting an erratic, missing, or out-of-range signal from the engine speed sensor that is mounted on the transmission housing. This sensor monitors the input speed to the transmission, and a failure can cause erratic shifting, loss of drive, or default to a limp-home mode.

• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626

1. 1

   Visually inspect the transmission-mounted speed sensor on the transmission housing for obvious physical damage or a loose mounting bolt.

2. 2

   Inspect the wiring harness leading to the sensor for chafed wires, melted insulation, or broken connections. Disconnect the sensor and check the pins for corrosion, moisture, or pushed-out terminals.

3. 3

   Using a multimeter, measure the resistance across the sensor pins (should read approximately 540 +/- ohms). An open circuit or dead short indicates a failed internal coil.

4. 4

   If the sensor is removed, use a borescope or flashlight to inspect the tone ring/gear inside the transmission housing for damaged or missing teeth, which can cause erratic signal values.

1. 1

   Preparation

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

2. 2

   Locate the Sensor

   Identify the faulty transmission-mounted engine speed sensor on the transmission housing (refer to your specific model's service manual for the exact port location).

3. 3

   Removal

   Depress the locking tab and disconnect the electrical harness from the sensor. Remove the retaining bolt/nut securing the sensor to the housing. Carefully pull the sensor straight out. (Have a rag ready, as a small amount of transmission fluid may weep from the port).

4. 4

   Cleaning

   Clean the mounting surface on the transmission housing to ensure the new sensor seats perfectly flat.

5. 5

   Installation

   Lubricate the O-ring on the new sensor with a small amount of clean transmission fluid. Insert the sensor into the port and install the retaining bolt. Tighten to OEM torque specifications.

6. 6

   Reconnection

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

7. 7

   Code Clearing & Testing

   Turn the key to the ON position. Use a diagnostic tool or the tractor's onboard dashboard interface to clear the 04.01.85 fault code. Start the tractor and perform a test drive to verify that the transmission shifts smoothly and the code does not return.