What is SPN 3216 FMI 21 & How to Solve It?

What is SPN 3216 FMI 21:

SPN 3216 FMI 21 indicates a high voltage condition in the Fuel Rail Pressure Sensor Circuit. This fault suggests that the ECM is receiving a voltage from the fuel rail pressure sensor that is higher than expected, which can affect fuel injection timing and lead to performance issues such as rough idling or poor acceleration.

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Why This Happens:

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

How to Fix It:

1. Inspect the fuel rail pressure sensor and wiring for damage.
   
2. Test the sensor’s voltage and resistance to ensure it is within the expected range.
   
3. Check wiring and connectors for visible damage or corrosion.
   
4. Replace the faulty sensor if necessary.
   
5. Verify the fuel system’s performance and inspect the fuel pump for malfunction.
   
   

How to Avoid It Before It Happens:

• Regularly inspect the fuel rail pressure sensor and wiring.
  
• Keep connectors clean and corrosion-free.
  
• Maintain stable fuel pressure and replace filters at recommended intervals.
  
• Perform routine diagnostic checks to monitor fuel system health.
  
• Clue’s Fuel Management services track fuel pressure systems to detect issues before they cause engine inefficiency.