The DOC inlet outlet pressure fault sheet is the official Detroit DD Series diagnostic for an implausible DOC inlet/outlet pressure comparison, stored under SPN 3251 FMI 21 for GHG14 calibrations. It records the monitored parameter DOC inlet/outlet pressure, exactly as published by TruckFaultCodes.com (© 2017).
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | Detroit DD Series diesel engines (EPA 2007-current) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | SPN 3251 / FMI 21 |
| Fault condition | Oxidation Catalyst (DOC) Inlet / Outlet Pressure – Not Plausible |
| Monitored parameter | DOC inlet/outlet pressure |
| Emissions calibration | GHG14 |
| Source / Publisher | TruckFaultCodes.com |
| Year / Revision | 2017 |
| Pages | 3 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification: SPN 3251, FMI 21
- Description and monitored parameter
- Typical enabling conditions
- Troubleshooting steps
- Component inspection and repair verification
DOC inlet outlet pressure troubleshooting steps
The sheet has the technician confirm the code, inspect the pressure sensors, ports and hoses across the diesel oxidation catalyst, and compare the readings against the diesel diagnostic tool before repairing the affected sensor, hose or wiring.
Applicable truck models
This code sheet applies to trucks powered by Detroit DD Series diesel engines built to the GHG14 emissions calibration; always match the SPN 3251 FMI 21 listing to the vehicle’s own engine family before repair. Confirm the emissions family on the vehicle emissions label, because aftertreatment and dosing hardware differs between the EPA07, EPA10 and GHG14 builds and a mismatched procedure can send you to the wrong component. For engine coverage and dealer service information, see the Detroit Diesel official website.
Who needs this DOC inlet outlet pressure manual
Fleet technicians and independent workshops that service Detroit DD Series engines use this inlet outlet pressure reference to confirm the code, its enabling conditions and the correct repair before replacing parts. It is written for the mechanic making the repair decision, not the driver, and pairs with the wiring diagrams and component removal procedures Detroit publishes in Power Service Literature.
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