Detailed guide for SPN 5309 FMI 20
Back to top ↑Temperature sensors in aftertreatment age slowly. Erratic readings can make the regen logic think conditions are wrong, even if the physical temps are fine.
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SPN 5309 FMI 20: DPF outlet temp sensor data drift – readings not rational
Quick Answer
DPF outlet temp sensor data drift – readings not rational
Code
SPN 5309 FMI 20
Severity
Warning
Applies to
Check OEM application
Can I drive?
Driving suitability is not established by this code alone.
Common Symptoms
- DPF temperature spikes
- Unclear regen progress
- Climate/ambient variations
Likely Causes
- Sensor aging/drift
- Exhaust buildup coating sensor
- Wiring noise
Common Fixes
- Check sensor wiring and sleeve
- Replace temp sensor if drift confirmed
- Verify real temp with scan tool
Full technical sections↓
What does SPN 5309 FMI 20 mean?
Back to top ↑DPF outlet temp sensor data drift – readings not rational
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