FMI 20 — Data drifted high
The value crept upward over time compared with where it should sit. Slow drift, not a sudden fault.
Common causes
- Aging or contaminated sensor
- Gradual restriction building in the system
- Bad reference voltage slowly out of range
What to test, in order
- Compare key-off values against ambient reference
- Check the 5 V reference under load
- Trend the value across several trips
- Clean or replace the sensor and re-baseline
Codes we document with FMI 20
SPN 3216 FMI 20Inlet NOx sensor drifted · InternationalSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · CATSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · DetroitSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · PACCARSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · MERCEDESSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · VolvoSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · MackSPN 3216 FMI 20SCR inlet NOx sensor data drifted high · CumminsSPN 3226 FMI 20Outlet NOx sensor drift · VolvoSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · CATSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · DetroitSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · InternationalSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · PACCARSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · MERCEDESSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · MackSPN 3226 FMI 20SCR outlet NOx sensor data drifted high · Cummins
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