Detailed guide for SPN 4363 FMI 18
Back to top ↑If dosing rate is low, NOx conversion drops and the truck starts the countdown.\n\nLook for crystals at fittings and around the doser.
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Share ↓SPN 4363 FMI 18Severity: Critical
SPN 4363 FMI 18: SCR dosing rate too low – DEF not injected as expected
Quick Answer
SCR dosing rate too low – DEF not injected as expected
Code
SPN 4363 FMI 18
Severity
Critical
Applies to
Check OEM application
Can I drive?
Driving suitability is not established by this code alone.
Common Symptoms
- SCR efficiency faults
- Inducement countdown risk
- Aftertreatment light
Likely Causes
- DEF crystallization/restriction
- Dosing valve failing
- DEF pump/pressure issues
Common Fixes
- Check DEF pressure and dosing command
- Inspect doser for crystals and blockage
- Fix heater/line issues causing freeze-ups
Full technical sections↓
What does SPN 4363 FMI 18 mean?
Back to top ↑SCR dosing rate too low – DEF not injected as expected
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