What is SPN 3216 FMI 18 & How to Solve It?

What is SPN 3216 FMI 18:

SPN 3216 FMI 18 indicates a fault with the Selective Catalytic Reduction (SCR) Injector Pressure Sensor Circuit – Data Valid But Above Normal Operating Range. This means the sensor is sending data that is higher than the normal expected range, signaling possible issues in the SCR injector pressure system, which controls the Diesel Exhaust Fluid (DEF) injection for emissions reduction.

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Why This Happens

Common causes include:

• Faulty or failing SCR injector pressure sensor.
  
• Blockages or restrictions in the DEF injection system.
  
• Wiring issues such as damaged or corroded connectors.
  
• Faulty Engine Control Module (ECM) or sensor calibration errors.
  
  

How to Fix It

To resolve this fault:

1. Inspect the SCR injector pressure sensor and wiring for damage or corrosion.
   
2. Check DEF injection lines for blockages or restrictions.
   
3. Test the sensor signal and replace if faulty.
   
4. Repair or replace damaged wiring or connectors.
   
5. Clear the fault code and verify system operation.
   
   

How to Avoid It Before It Happens

Prevent this fault by:

• Regularly inspecting the DEF system sensors and wiring.
  
• Maintaining clean and clear DEF injection lines.
  
• Performing routine diagnostics to catch sensor issues early.
• Use Clue’s Preventive Maintenance to schedule regular inspections of the DEF system and ensure timely maintenance of the SCR injector pressure sensor and wiring.