This Fuel Cutoff Valve pressure sheet documents Detroit SPN 3480 FMI 21, a not-plausible reading on the hydrocarbon doser fuel compensation pressure that carries a 25 percent derate. It orders the checks from other fuel faults through leak inspection to component replacement. Follow it in sequence.
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | DD Series (EPA 2007-Current); also filed under Series 60 (DDEC VI – EPA 2007) |
| System / Group | DTCs — Fuel Cut-off Valve Pressure Not Plausible |
| Fault code | SPN 3480 / FMI 21 |
| Source | www.TruckFaultCodes.com (© 2017) |
| Pages | 3 |
| File size | 0.4 MB |
| Format | |
| Language | English |
Fuel Cutoff Valve pressure diagnostic guide
After safing the vehicle and connecting the diagnostic tool, the technician first clears any fuel system faults or SPN 3480 FMI 0, 3, 4 or 5, then inspects the HC doser block and injector fuel lines for external leaks. The chart decides the repair: a Gen 1 system gets a new fuel compensation pressure sensor while a Gen 2 system gets a new metering unit. A doser purge, taking up to three attempts, and a parked regeneration confirm the fix; a code that returns during regeneration means retaining the log and calling the support centre.
Document table of contents
- Fault code identification: SPN 3480, FMI 21
- Description, monitored parameter and 25 percent derate
- Step-by-step troubleshooting procedure
- External leak inspection and component chart
- Doser purge, parked regeneration and verification
Applicable truck models
This procedure applies to Detroit DD Series engines built for EPA 2007 and later, covering GHG14 calibrations as printed on the document cover, and the identical SPN/FMI sheet is also filed under Detroit Series 60 (DDEC VI, EPA 2007). Confirm the emissions platform on your truck and cross-check the connector and pin numbers against the official Detroit engine support site before making any repair.
Who needs this Fuel Cutoff Valve pressure manual
A diesel technician on a GHG14 Detroit engine with a doser pressure complaint and heavy derate uses this sheet to order the checks correctly and choose between a sensor and a metering unit by system generation.
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