What is SPN 3521 FMI 31 & How to Solve It?

What is SPN 3521 FMI 31:

SPN 3521 FMI 31 refers to a high voltage condition in the Fuel Pressure Sensor Circuit. This issue indicates that the ECM is receiving a voltage higher than expected from the fuel pressure sensor, which can cause inaccurate fuel pressure readings and affect the fuel delivery system.

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Why This Happens:

• Faulty fuel pressure sensor.
  
• Damaged or shorted wiring in the sensor circuit.
  
• Loose or corroded sensor connectors.
  
• High voltage supply to the sensor.
  
• ECM misinterpreting the sensor’s signal.
  
  

How to Fix It:

1. Inspect the fuel pressure sensor for damage or malfunction.
   
2. Test the voltage and resistance from the sensor to ensure it is within specification.
   
3. Check the wiring and connectors for damage or corrosion.
   
4. Replace the faulty sensor if it is providing inaccurate readings.
   
5. Ensure the voltage supply to the sensor is stable and within range.
   
   

How to Avoid It Before It Happens:

• Perform regular inspections of the fuel pressure sensor and wiring.
  
• Ensure proper voltage supply to the sensor to prevent high voltage conditions.
  
• Keep connectors clean and corrosion-free.
  
• Perform diagnostic checks to monitor fuel pressure system performance.
  
• Clue’s Fuel Management services provide ongoing monitoring of fuel pressure to detect issues before they cause performance problems.