What is SPN 5435 FMI 7 & How to Solve It?

What is SPN 5435 FMI 7:

SPN 5435 FMI 7 indicates a fault with the Selective Catalytic Reduction (SCR) Catalyst Temperature Sensor – Signal Too High. This means the sensor is reporting a temperature higher than the expected range, which can affect the SCR system’s ability to reduce nitrogen oxide emissions effectively.

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Why This Happens

Common causes include:

• Faulty SCR catalyst temperature sensor.
  
• Wiring issues such as short circuits or damaged connectors.
  
• Sensor contamination or physical damage.
  
• Excessive exhaust temperatures causing sensor failure.
  
  

How to Fix It

To resolve this fault:

1. Inspect the SCR catalyst temperature sensor and wiring for damage or corrosion.
   
2. Test the sensor’s resistance and voltage.
   
3. Replace the sensor if faulty.
   
4. Repair or replace damaged wiring or connectors.
   
5. Clear the fault code and monitor SCR system performance.
   
   

How to Avoid It Before It Happens

Prevent this fault by:

• Regularly inspecting the SCR catalyst temperature sensor and wiring.
  
• Avoiding excessive exhaust temperatures through proper engine operation.
  
• Performing routine diagnostics to detect sensor issues early.
• Use Clue’s Preventive Maintenance to schedule regular checks of the SCR catalyst temperature sensor and wiring, ensuring proper functionality and early detection of issues.