Code Details
| Display code | SPN 3055 FMI 14 |
|---|---|
| SPN | 3055 |
| FMI | 14 |
| OEM code | None listed |
| Manufacturer | Detroit Diesel |
| System | Aftertreatment �?DPF |
| Component | DPF / aftertreatment system / regeneration system |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
The DD15 DPF regeneration system normally completes soot burn-off during highway driving when exhaust temperatures are adequate. When the soot load becomes too high for a driving regen, the system requests a parked regen. SPN 3055 FMI 14 is the formal fault indicating this requirement. On Freightliner Cascadia, this is displayed as a DPF regen required warning, typically with a yellow lamp and a driver message. If ignored, the system will escalate to a derate and eventually a reduced speed operation.
SPN 3055 FMI 14 is Aftertreatment DPF Condition �?parked regen required. On Detroit DD15 GHG14 and GHG17, the aftertreatment control monitors DPF pressure differential to calculate soot load. DiagnosticLink shows the current soot load percentage, regen history, and can initiate a forced parked regen remotely during service. The escalation sequence for GHG17 DD15 engines may differ from GHG14 in terms of derate thresholds and regen initiation prompts.
Common Symptoms
- DPF regen required warning lamp on the Cascadia or Western Star dash
- Possible engine speed or power limitation
- Higher exhaust smoke during parked regen initiation
- Associated low-speed or stop-and-go operation history
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Extended city driving or short trips that prevent highway-temperature regen cycles
- Driver repeatedly inhibiting regen requests at inopportune times
- DPF pressure differential sensor reading high due to fault
- Previous incomplete regen cycles leaving residual soot
First Checks
- Initiate a parked regen per the Cascadia/Western Star driver display procedure in a safe, ventilated outdoor area
- Connect DiagnosticLink to monitor DPF soot load percentage and regen progress
- After parked regen completion, verify soot load has returned to normal range in DiagnosticLink
- If parked regen fails to complete, check DPF condition and pressure differential sensor function
- Review DiagnosticLink regen history to understand the frequency and duration of recent regen cycles
Can I Keep Driving?
Driveable but with increasing derate severity if regen is not completed. Address as soon as safely possible.
Related Codes
Related Lookup Pages
Sources
- Detroit Diesel Service and Diagnostic Resources — Public Reference Detroit Diesel (Daimler Truck North America) · oem · accessed 2026-06-11 · confidence medium
Source: Detroit Diesel (Daimler Truck North America), Detroit Diesel Service and Diagnostic Resources — Public Reference. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - DiagnosticLink Detroit Diesel Corporation · oem · accessed 2026-05-05 · confidence medium
Source: Detroit Diesel Corporation, DiagnosticLink. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
What is the difference between a driving regen and a parked regen on the Detroit DD15?
A driving regen occurs automatically at highway speeds when exhaust temperatures are sufficient for passive soot oxidation or mild active regen. A parked regen is an active cycle initiated when driving conditions cannot provide adequate regen conditions. During a parked regen, the engine runs at elevated idle to maintain DPF temperature for 20�?0 minutes until the soot is burned off.
Can DiagnosticLink force a parked regen on the DD15 from the shop?
Yes. DiagnosticLink with the appropriate access level can initiate a forced stationary regen on the DD15. This is useful in a service environment to complete a regen when the driver cannot easily do so, or to verify DPF function after a repair. The vehicle must be parked outdoors with the parking brake set and exhaust free of obstruction.
Does the DD15 parked regen escalation differ between GHG14 and GHG17?
Yes. GHG17 DD15 engines have updated aftertreatment calibration with revised escalation sequences and derate thresholds. The driver warnings, derate levels, and distance-to-derate values can differ between GHG14 and GHG17. DiagnosticLink displays the current calibration level and the specific thresholds applicable to the particular engine.