SPN 4364 — Aftertreatment 1 SCR Conversion Efficiency
System: Aftertreatment / SCR
How well the SCR system is reducing NOx compared with what it should be doing.
Can I keep running it?
HIGH — limit use, diagnose now
Low SCR efficiency leads to inducement derates and a speed limit. Diagnose soon.
Likely causes
- Poor DEF quality
- DEF doser clogged or crystallized
- Faulty NOx sensor
- Exhaust leak
- Aged or contaminated SCR catalyst
Checks & fixes (easiest first)
- Test DEF concentration
- Inspect and clean the doser for crystals
- Run the OEM DEF dosing quantity test
- Verify NOx sensor readings
- Check for exhaust leaks
Common FMIs with SPN 4364
- SPN 4364 FMI 1Value too low (most severe)
- SPN 4364 FMI 18Value too low (moderately severe)
Related codes
- SPN 3216Aftertreatment 1 Intake NOx
- SPN 3226Aftertreatment 1 Outlet NOx
- SPN 3364Aftertreatment 1 DEF Quality
- SPN 5246Aftertreatment SCR Operator Inducement Severity
FAQ
What does SPN 4364 mean?
SPN 4364 is Aftertreatment 1 SCR Conversion Efficiency. How well the SCR system is reducing NOx compared with what it should be doing.
Can I keep running with SPN 4364?
Low SCR efficiency leads to inducement derates and a speed limit. Diagnose soon.
What causes SPN 4364?
Poor DEF quality; DEF doser clogged or crystallized; Faulty NOx sensor; Exhaust leak; Aged or contaminated SCR catalyst.