What is SPN 2791 FMI 7 & How to Solve It?

What is SPN 2791 FMI 7:

SPN 2791 FMI 7 indicates a fault with the Selective Catalytic Reduction (SCR) Urea Dosing Valve Circuit – Signal Too High. This means the engine control module (ECM) has detected a voltage or signal from the urea dosing valve that is higher than the expected range, potentially affecting the Diesel Exhaust Fluid (DEF) injection process and emissions control.

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Why This Happens

Common causes include:

• Faulty or damaged urea dosing valve.
  
• Wiring issues such as short circuits or damaged connectors.
  
• Contaminated or degraded DEF fluid impacting valve function.
  
• Faulty ECM or sensor calibration errors.
  
  

How to Fix It

To resolve this fault:

1. Inspect the urea dosing valve and wiring for damage or corrosion.
   
2. Test the valve operation and replace if faulty.
   
3. Replace contaminated DEF fluid if needed.
   
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:

• Using clean, high-quality DEF fluid.
  
• Regularly inspecting the urea dosing valve and wiring.
  
• Keeping the DEF system clean and well-maintained.
• Leverage Clue’s Asset Tracking to monitor the urea dosing valve’s performance and identify issues early, ensuring proper emissions control.