9 Detroit Diesel diagnostic codes on file — with the full diagnosis, repair steps, and field insights open to read free, no signup required.
Disclaimer: General reference information for trained, qualified technicians only. Codes and procedures vary by model, serial number and software version. Always follow the manufacturer's service manual and your site's safety procedures. Use at your own risk. Not affiliated with or endorsed by any manufacturer.
| Code | System | Symptom | Full fix |
|---|---|---|---|
| SPN 3226 FMI 20 | Emissions / NOx | Check Engine Light / Inducement Risk | View fix |
| SPN 3482 FMI 5 | Emissions / Fuel | Parked Regen Fails to Initiate | View fix |
| SPN 3719 FMI 0 | Emissions / DPF | Active DPF Lamp / Torque Derate | View fix |
| SPN 4334 FMI 4 | Emissions / DEF | Active 5 MPH Derate / DEF Lamp Solid | View fix |
| SPN 4364 FMI 18 | Emissions | DEF Light Active / Heavy Derate | View fix |
| SPN 520371 FMI 16 | Emissions | MIL On / Elevated DEF Consumption | View fix |
| SPN 520372 FMI 16 | Emissions | Progressive 5 MPH Inducement Derate | View fix |
| SPN 5246 FMI 0 | Emissions | Immediate 5 MPH Lockout Derate | View fix |
| SPN 5397 FMI 31 | Emissions / DPF | Active DPF Light / High Fuel Burn | View fix |
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