What is SPN 5319 FMI 31 & How to Solve It?

What is SPN 5319 FMI 31:

SPN 5319 FMI 31 indicates a fault with the Selective Catalytic Reduction (SCR) Catalyst Temperature Sensor Circuit – Electrical Fault (High Resistance or Open Circuit). This means the sensor circuit has a high resistance or an open connection, which can cause inaccurate temperature readings and affect the SCR system's ability to reduce emissions effectively.

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Why This Happens

Common causes include:

• Damaged or corroded wiring/connectors causing high resistance or open circuit.
  
• Faulty SCR catalyst temperature sensor.
  
• Physical damage or contamination of the sensor.
  
• Faulty Engine Control Module (ECM).
  
  

How to Fix It

To resolve this fault:

1. Inspect the SCR catalyst temperature sensor wiring and connectors for damage or corrosion.
   
2. Test the sensor and replace if faulty.
   
3. Repair or replace damaged wiring or connectors.
   
4. Clear the fault code and verify sensor and SCR system operation.
   
   

How to Avoid It Before It Happens

Prevent this fault by:

• Regularly inspecting sensor wiring and connections.
  
• Keeping the SCR system clean and well-maintained.
  
• Performing routine diagnostics to detect wiring or sensor issues early.