The Detroit crankcase breather speed document is a Detroit fault code reference that explains an engine crankcase breather oil separator speed that is too low, published for DD Series engines under SPN 5444 FMI 1 (All Years). It gives workshop technicians the diagnostic sequence used to confirm the condition and return the truck to service, sourced from Detroit Power Service Literature.
Official document details
| Brand | Detroit (Detroit Diesel) |
| Model coverage | DD Series (EPA 2007-Current) and Series 60 (DDEC VI) |
| System / Group | Diagnostic Trouble Codes (DTCs) |
| Fault code | SPN 5444 / FMI 1 |
| Emissions family | All Years |
| Pages | 3 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification — SPN 5444 / FMI 1
- Oil separator vent leakage inspection
- Breather speed sensor connector inspection
- MCM 120-pin resistance and voltage checks
- Crankcase breather speed verification
Troubleshooting the Detroit crankcase breather speed code
The routine inspects the crankcase oil separator vent for oil leakage, then checks the breather speed sensor connector for pin damage and cleans the sensor and mounting cavity. Voltages and resistances are measured at the sensor harness and the MCM 120-pin connector to find a shorted, open or grounded wire, and the technician monitors crankcase oil separator speed above 1500 rpm engine speed, contacting the Detroit Customer Support Center with a log file if the speed does not rise as expected.
Applicable truck models and engines
This diagnostic sheet applies to Detroit DD Series diesel engines built to EPA 2007 through current emissions standards, and the covered fault also appears on Series 60 (DDEC VI) applications listed in the source. Confirm the exact engine family and calibration against the vehicle before making repairs, and cross-check the specifications on the official Demand Detroit website.
Who needs this Detroit crankcase breather speed manual
Heavy-duty truck technicians, fleet maintenance staff and workshop owners diagnosing SPN 5444 FMI 1 with a diesel diagnostic tool will use this sheet to follow the correct steps rather than replacing parts by guesswork.
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