Detroit fault code SPN 3031 FMI 10 is the TruckFaultCodes.com diagnostic sheet for the Diesel Exhaust Fluid (DEF) Tank Temperature Erratic condition on Detroit DD-series engines. This 2 pages reference lists the fault identification, monitored conditions where shown, and the step-by-step troubleshooting the technician follows in the shop.
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Publication no. | Not printed; TruckFaultCodes.com reference |
| Year / Revision | 2017 |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (SPN 3031 / FMI 10)
- Cooling system check
- Output Component Test
- AS021 temperature comparison
- DEF tank header inspection and replacement
SPN 3031 FMI 10 troubleshooting steps
The two-page routine first addresses any cooling system complaints, then connects the diesel diagnostic tool and runs the Output Component Test, which can only run once per key cycle. Parameter AS021 DEF Tank Temperature is monitored and compared against an external thermometer reading taken through the filler; a difference greater than 10 C (50 F) points to a fault. The DEF tank header temperature or coolant valve connector is inspected for bent, spread or corroded pins, and the DEF tank header assembly is replaced when no pin damage is found.
Applicable truck models
This sheet applies to Detroit DD-series diesel engines (the DD13, DD15 and DD16 family) built under the EPA 2007-Current emissions platform, in its GHG14 calibration. Engine and emissions specifications should always be confirmed against the vehicle build; full engine information is published on the Detroit Diesel official site.
Who needs this SPN 3031 FMI 10 manual
Technicians seeing an erratic DEF tank temperature reading use this sheet to compare the reported value against an actual measurement before replacing the tank header. It is a quick bench reference rather than a full workshop manual, so the named removal steps still route back to Power Service Literature and, where escalation is needed, to the Detroit Customer Support Center.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download it.
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