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Detroit Diesel SPN 3364 FMI 2 indicates a Diesel Exhaust Fluid (DEF) quality or sensor fault. This code commonly appears when the DEF concentration is incorrect or when the DEF sensor is malfunctioning.
Symptoms
- Check engine light illuminated
- DEF warning message
- Engine derate countdown
- Reduced power
Cause
This fault is typically triggered by contaminated DEF, incorrect DEF concentration, failed DEF quality sensor, or wiring issues within the aftertreatment system.
Can You Keep Driving?
Driving may be possible temporarily, but continued operation can lead to progressive derate and eventual speed limitation if not addressed.
Recommended Action
Inspect DEF quality and ensure correct fluid concentration. Replace contaminated DEF if necessary. If the issue persists, perform diagnostic testing on the DEF sensor and wiring.
Common causes include contaminated DEF fluid, incorrect DEF concentration, sensor failure, wiring issues, or crystallization buildup in the DEF tank.
SPN 3364 FMI 2 indicates that the Diesel Exhaust Fluid (DEF) quality sensor is reporting an out-of-range or erratic signal.
Driving may be possible temporarily, but unresolved DEF quality faults can trigger progressive engine derate.
Yes. If the DEF issue is not corrected, the engine control module may limit vehicle speed to comply with emissions regulations.
How do I fix SPN 3364 FMI 2?
Need Immediate Help With This Fault Code?
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Important Notice
The information provided above is for general informational purposes only and should not replace official OEM service procedures. Always consult the manufacturer’s service manual or a qualified diesel technician before performing repairs. Operating a vehicle with active fault codes may result in further damage.