Massey Ferguson 04.00.91 – TRANS1: Issue With Speed Sensor Values (TRANS1)

The transmission control system is receiving erratic, implausible, or missing signals from one of the transmission speed sensors (such as the forward speed sensor, intermediate speed sensor, or output speed sensor). Because the controller relies on these values to manage clutch engagement and shifting, a failure here can result in transmission slippage, erratic shifting, or the tractor defaulting to emergency limp mode.

• 7724S
• 5712SL
• 7722
• 7722S
• 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

   Connect the tractor to the Massey Ferguson Wintest diagnostic software and monitor the active and requested values of the transmission speed sensors (e.g., TR4, TR25) while driving to identify which sensor is dropping the signal.

2. 2

   Disconnect the suspect induction sensor and measure the resistance across Pin 1 (Signal) and Pin 2 (Ground). A healthy sensor reads 450 Ohms (+/- 20 Ohms) when stopped. An infinite reading indicates an open circuit.

3. 3

   Check for an alternating voltage (AC) signal coming from the sensor when the internal pinion/shaft is rotating.

4. 4

   Inspect the wiring harness leading to the TRANS1 module for open circuits, or short circuits to ground (0V) or +12V.

1. 1

   Locate the Sensor

   Locate the faulty speed sensor on the transmission housing (often located close to the gearbox cover).

2. 2

   Removal

   Disconnect the electrical connector and unscrew the sensor from the transmission casing.

3. 3

   Preparation

   Clean the mounting port. Apply a small amount of thread sealant (such as Loctite 5922) to the threads of the new sensor.

4. 4

   Installation & Air-Gap Adjustment

   Screw the new sensor in until it bottoms out (in abutment) against the internal pinion gear.

5. 5

   Set the Gap

   Once it touches the gear, back the sensor out slightly (usually 1/2 to 3/4 of a turn) to establish the correct air gap. Secure it in place with the locking nut.

6. 6

   Reassembly

   Reconnect the wiring harness, clear the 04.00.91 fault code using the diagnostic tool, and test drive the tractor to verify the speed values are reading correctly.