Massey Ferguson 4201.31 – Engine Control Unit (ECU): Crankshaft Speed Sensor Signal Issue

Crankshaft speed sensor signal missing. The engine management system relies on this sensor to read a trigger wheel to determine the crankshaft's position and rotational speed. If the pulses are not received at the correct time, or the signal drops out entirely, the Time Processing Unit (TPU) logs this fault, usually resulting in engine power degradation or a forced shutdown.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724
• 5400
• 6400
• 7400
• 6480
• 7465
• 7480

1. 1

   Inspect the sensor wiring harness for chafing, breaks, or short circuits, and check the connector for corrosion, moisture, or backed-out pins

2. 2

   Rule out fuel supply issues, poor fuel quality, or misfiring that could cause mechanical stuttering, as rough engine running can falsely flag a missing signal

3. 3

   Test the sensor's resistance with a multimeter to see if it has failed internally (open circuit)

4. 4

   Ensure the trigger wheel (viewable through the sensor mounting hole) is not damaged, covered in metallic debris, or missing teeth

1. 1

   Preparation

   Turn off the engine, remove the key, and allow the engine to cool. Disconnect the negative battery terminal.

2. 2

   Locate the Sensor

   Locate the crankshaft speed sensor on the lower engine block, typically positioned near the crankshaft pulley or the flywheel housing.

3. 3

   Removal

   Depress the locking tab and disconnect the electrical pigtail from the sensor. Remove the retaining bolt holding the sensor to the engine block. Carefully pull the sensor straight out. (If it is stuck, twist gently; do not pry aggressively to avoid breaking the plastic tip inside the block).

4. 4

   Inspection & Cleaning

   Wipe the mounting port clean. Shine a flashlight into the hole to verify the trigger wheel is free of heavy debris.

5. 5

   Installation

   Lubricate the O-ring on the new sensor with a drop of clean engine oil. Insert the new sensor into the port until it seats flush. Install and tighten the retaining bolt to the manufacturer's torque specification (usually snug, do not overtighten).

6. 6

   Reconnection

   Plug the electrical connector back in until it clicks securely. Reconnect the battery.

7. 7

   Clear Codes

   Use an AGCO diagnostic tool (such as WinEEM3/WinEEM4 Service Tool or Massey Ferguson WinTest) to clear the inactive 004201.31 code from the ECU memory. Run the engine to verify the code does not return.