SPN 3242 FMI 20 is the Detroit DD Series (EPA 2007-current) diagnostic fault sheet for the DOC temperature drift — inlet high or outlet low condition on the DOC temperature sensor circuit. It diagnoses a temperature drift by comparing the DOC inlet temperature against the DOC outlet and DPF outlet temperatures, then inspecting the affected sensor harness and measuring pigtail resistance to isolate the drifting sensor. The sheet is written for heavy-duty technicians who pull this diagnostic trouble code with a diesel diagnostic tool and need the confirmed factory step order rather than guesswork.
SPN 3242 FMI 20 document details
| Brand | Detroit (Detroit Diesel) |
| Model coverage | DD13, DD15 and DD16 — DD Series (EPA 2007-current) |
| System / Group | DOC temperature sensor / DTCs |
| Fault code | SPN 3242 / FMI 20 |
| Emissions platform | EPA10/GHG14 |
| Source | TruckFaultCodes.com fault-code reference (© 2017) |
| Pages | 3 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification — SPN 3242, FMI 20
- DOC temperature drift — inlet high or outlet low
- Comparing DOC inlet, DOC outlet and DPF outlet temperatures
- Harness inspection and pigtail resistance test
- Sensor replacement per Power Service Literature
Applicable truck models
This DOC temperature drift — inlet high or outlet low procedure applies to Detroit DD13, DD15 and DD16 engines built on the DD Series (EPA 2007-current) aftertreatment platform (EPA10/GHG14 calibrations) and is cross-listed for Series 60 DDEC VI (EPA 2007) installations that share the same DOC temperature sensor. Removal and installation callouts refer to Detroit Power Service Literature, and the Detroit Customer Support Center (800-445-1980) is the authoritative escalation point. Full model and engine coverage is confirmed on the Detroit Diesel official website.
Who needs this SPN 3242 FMI 20 manual
Workshop owners, mobile diesel technicians and fleet maintenance teams reach for this manual the moment a scan tool reports SPN 3242/FMI 20. It keeps the diagnosis on the manufacturer’s confirmed path, which shortens repair time and avoids replacing a good DOC temperature sensor. The complete PDF is available in the DiagTechPro manuals library; a free account is required to download it.
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