What is SPN 723 FMI 8 & How to Solve It?

What is SPN 723 FMI 8:

SPN 723 FMI 8 indicates a fault with the Aftertreatment 1 Diesel Exhaust Fluid (DEF) Injector Control Circuit - Voltage Below Normal or Shorted to Low. This means the engine control module (ECM) is detecting that the voltage in the DEF injector control circuit is lower than expected, which can prevent proper DEF injection and reduce the effectiveness of emissions control.

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Why This Happens

Common causes include:

• Faulty DEF injector or injector control module.
  
• Damaged, shorted, or corroded wiring or connectors in the DEF injector circuit.
  
• Faulty ECM not properly controlling the injector circuit.
  
• Contamination or clogging in the DEF injector.
  
  

How to Fix It

To resolve this fault:

1. Inspect the DEF injector and associated wiring for damage or corrosion.
   
2. Test the DEF injector control circuit voltage and replace components if faulty.
   
3. Repair or replace damaged wiring or connectors.
   
4. Clean or replace the DEF injector if clogged.
   
5. Clear the fault code and verify injector operation.

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How to Avoid It Before It Happens

Prevent this fault by:

• Regularly inspecting the DEF injector and wiring.
  
• Using high-quality DEF fluid to prevent clogging.
  
• Performing routine maintenance and diagnostics to catch issues early.
• Use Clue’s Preventive Maintenance to schedule regular checks on the DEF injector, wiring, and system to ensure optimal performance and avoid potential issues with emissions control.