Massey Ferguson 4.02.90 – Transmission Control Module (TRANS1): Issue With Speed Sensor Values (TRANS1)

The control module is receiving an erratic, out-of-range, or missing signal from the transmission speed sensor. Without accurate speed data, the transmission may experience shifting problems, default to a limp mode, or fail to calibrate properly.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• T4
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S

1. 1

   Inspect the wiring harness and connector leading to the transmission speed sensor for chafing, corrosion, or loose pins.

2. 2

   Disconnect the sensor and measure the resistance across the sensor pins (Pin 1: Signal, Pin 2: Ground). A healthy inductive speed sensor typically reads between 450 Ohms (+/- 20) and 540 Ohms.

3. 3

   Check for alternating AC voltage output from the sensor pins while the transmission pinion/shaft is rotating.

4. 4

   Check the air gap if the sensor was recently replaced or backed out, as an incorrect gap leads to weak signal generation.

1. 1

   Locate the Sensor

   Locate the transmission speed sensor on the transmission housing (gearbox cover).

2. 2

   Remove the Old Sensor

   Disconnect the electrical connector and unscrew the faulty sensor from the housing.

3. 3

   Prep the New Sensor

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

4. 4

   Set the Air-Gap

   Carefully screw the new inductive sensor into the housing until it bottoms out (in abutment) on the internal pinion gear. Once it touches, back the sensor out slightly according to the specific transmission manual's air-gap specification to prevent physical damage while allowing a strong signal.

5. 5

   Reassemble

   Tighten the lock nut to secure the sensor in place and reconnect the electrical harness.

6. 6

   Clear Codes

   Use a diagnostic scan tool to clear the 4.02.90 fault code and test drive the tractor to verify that the transmission shifts correctly and the code does not return.