Detailed guide for SPN 4334 FMI 18
Back to top ↑Low DEF pressure quickly turns into SCR efficiency faults and derates.\n\nLook for white crystals at fittings. They are the system leaving you clues.
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Share ↓SPN 4334 FMI 18Severity: Critical
SPN 4334 FMI 18: DEF dosing pressure below normal (weak pump or restriction)
Quick Answer
DEF dosing pressure below normal (weak pump or restriction)
Code
SPN 4334 FMI 18
Severity
Critical
Applies to
Check OEM application
Can I drive?
Driving suitability is not established by this code alone.
Common Symptoms
- Inducement countdown risk
- SCR efficiency faults
- May derate after a few drive cycles
Likely Causes
- DEF pump weak
- Restriction or crystallization
- Leaks at DEF line or fittings
Common Fixes
- Inspect for DEF leaks and crystals at fittings
- Verify command vs actual pressure
- Clean/replace restricted components as needed
Full technical sections↓
What does SPN 4334 FMI 18 mean?
Back to top ↑DEF dosing pressure below normal (weak pump or restriction)
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