Massey Ferguson 520389.31 – Engine Control Unit (ECU): Issue With The Air Intake Mass Air Flow Sensor (ECU)

Air mass sensor value not plausible. The controller is receiving a signal from the Mass Air Flow (MAF) sensor that falls outside the logical or expected range for the engine's current operating state.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• MF 8700 S Series
• MF 8727 S
• MF 8730 S
• MF 8732 S
• MF 8735 S
• MF 8737 S
• MF 8740 S Dyna-VT
• MF IDEAL 7
• MF IDEAL 8
• MF IDEAL 9
• MF 7370 ST5
• MF Beta 7370 PLI

1. 1

   Check for related codes that might isolate the issue, such as 520390.31 (Air mass sensor start test time exceeded) or 520391.31 (Air mass sensor start test value not plausible/too high)

2. 2

   Inspect the MAF sensor's electrical connector and wiring harness, and verify the machine's ground reference to rule out poor grounds or open circuits

3. 3

   Inspect the entire air control system (pre-filter, main air filter, intercooler, and air pipes) for blockages, heavy dust accumulation, or unmetered air leaks between the filter and the turbocharger

1. 1

   Preparation

   Turn off the machine's engine and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the Mass Air Flow (MAF) sensor within the air control system. It is typically mounted on the intake piping routed from the air filter to the low-pressure turbocharger.

3. 3

   Disconnect

   Carefully unplug the electrical connector from the MAF sensor.

4. 4

   Removal

   Loosen the clamps or retaining screws securing the MAF sensor to the air pipe and remove the faulty sensor.

5. 5

   Installation

   Clean the mounting area, ensuring no dirt or debris falls into the intake tract (which could damage the turbocharger). Install the new AGCO MAF sensor in the correct airflow direction.

6. 6

   Reassembly

   Secure the sensor housing and plug the electrical connector back in until it clicks.

7. 7

   Clear Codes

   Reconnect the battery, turn on the machine, and use a specialized diagnostic tool to clear the inactive DTC codes from the ECU.