SPN 677 FMI 31 is the Detroit DD Series diagnostic fault code that identifies Starter jammed (tooth to tooth jam). This DiagTechPro reference summarizes the official 1-page Detroit diagnostic sheet so a technician can confirm the condition before opening the truck, and it links to the full downloadable PDF.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) diesel engines |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault condition | Starter jammed (tooth to tooth jam) |
| Published source | TruckFaultCodes.com, Copyright © 2017 |
| Pages | 1 |
| File size | 0.2 MB |
| Format | |
| Language | English |
SPN 677 FMI 31 diagnostic overview
This one-page Detroit sheet describes a starter jammed in a tooth-to-tooth condition, meaning the starter teeth did not engage correctly into the flywheel. The technician attempts to start the engine, and if it starts correctly repeats the start three times; if the fault does not return the code is cleared and the vehicle is released. When the starter still fails to engage the flywheel, the sheet lists possible causes: starter motor alignment, starter drive damage, an incorrect starter installed, or flywheel damage.
Document table of contents
- Fault code identification
- Starter engagement note
- Repeat-start verification
- Possible causes of tooth-to-tooth jam
Applicable truck models covered
This diagnostic applies to Detroit DD Series (EPA 2007-Current) diesel engines across all model years, and is also grouped under the Series 60 (DDEC VI – EPA 2007) DTCs. It covers the mechanical engagement between the starter drive and the flywheel ring gear. For the OEM wiring schematics referenced in this procedure, see the official Detroit engine manufacturer site.
Who needs the SPN 677 FMI 31 manual
Workshop technicians and fleet owners using the diesel diagnostic tool to read Detroit fault codes and test the starter drive and Motor Control Module wiring will need this sheet. The full step-by-step PDF is available in the DiagTechPro manuals library, and a free account is required to download it.
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