Detroit fault code SPN 3031 FMI 4 is the TruckFaultCodes.com diagnostic sheet for the Diesel Exhaust Fluid (DEF) Tank Temperature Sensor Circuit Failed Low condition on Detroit DD-series engines. This 1 page 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 | 1 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (SPN 3031 / FMI 4)
- Sensor disconnect and pin inspection
- ACM 120-pin resistance measurement
- Short-to-ground repair or sensor replacement
SPN 3031 FMI 4 troubleshooting steps
With the ignition off, the DEF tank temperature and level sensor is disconnected and its harness is inspected for bent, spread or corroded pins. The ACM 120-pin connector is then disconnected and resistance is measured between pin 3 of the sensor harness connector and ground. A reading below 1k ohm indicates a short to ground between that pin and pin 103 of the ACM 120-pin connector, which is repaired; otherwise the DEF tank temperature and level sensor is replaced.
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 EPA10 / 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 4 manual
Technicians with a DEF tank temperature sensor circuit reading low use this sheet to confirm a harness short to ground before replacing the sensor. 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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