4 Cummins 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 |
|---|---|---|---|
| Cummins 221 | Air Intake | Engine Derate / Active CEL | View fix |
| SPN 132 FMI 2 | Air Intake | Black Smoke / Engine Sags | View fix |
| SPN 641 FMI 7 | Air Intake | Low Boost / Heavy Sluggish Pick-up | View fix |
| SPN 641 FMI 7 | Air Intake | Low Boost / Sluggish Acceleration | View fix |
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