This Detroit SCR air pressure document covers fault code SPN 4335 / FMI 1 on EPA10 engines, where DEF air pressure is not detected from the vehicle supply and the engine derates 25%. The eight-page procedure runs from vehicle air checks through gauge tests to flushing DEF crystals from the metering unit.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD-Series (DD13, DD15, DD16) and Series 60 (DDEC VI) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | SPN 4335 / FMI 1 |
| Fault name | DEF air pressure not detected (from vehicle supply) |
| Emissions platform | EPA10 |
| Pages | 8 |
| File size | 0.5 MB |
| Format | |
| Language | English |
| Source | TruckFaultCodes.com (© 2017); Detroit Power Service Literature |
Detroit SCR air pressure sections covered
The long routine walks the whole air path, from the tank and pressure limiting unit to the metering unit diffuser and supply screen.
- Confirm vehicle air pressure reaches 689 kPa (100 psi)
- Compare DEF air pressure to barometric (Baro) and DEF pressure
- Inspect air supply lines and pressure limiting unit orifices
- Gauge the SCR test at 537 to 586 kPa (78 to 85 psi)
- Inspect and flush the compressed air supply screen and diffuser heater
- Verify 131 to 200 kPa (19 to 29 psi) or contact Detroit support
Applicable truck models
This procedure covers Detroit DD-Series (DD13, DD15 and DD16) and Series 60 DDEC VI engines on the EPA10 platform served by the ACM2 aftertreatment control module. Removal and flushing steps and the DEF test kit reference are in Detroit Power Service Literature at the Detroit Diesel official website.
Who needs this Detroit SCR air pressure manual
This SCR air pressure manual is for the technician facing a full no-air condition on SPN 4335 / FMI 1, where the eight-page path through the air system and crystal flush is what a 25% derate demands.
The full 8-page PDF is available in the DiagTechPro manuals library; a free account is required to download. For workshop reference, Detroit documents the matching component removal and installation steps for SPN 4335 / FMI 1 in Power Service Literature, and technicians should keep the wiring pin numbers shown in this sheet on hand while testing on the bench.
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