SPN 3364 FMI 9 indicates SCR efficiency problems which may lead to derate.
Symptoms
- Derate warning
- Check engine light
- Frequent regen
- DEF issues
Common Causes
- Bad NOx sensors
- DEF issues
- SCR failure
- Wiring issues
How to Fix
- Check NOx sensors
- Check DEF quality
- Run diagnostics
- Repair components