SPN 677 FMI 3 is the Detroit DD Series diagnostic fault code that identifies Engine starter relay shorted to high source. 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 | Engine starter relay shorted to high source |
| Published source | TruckFaultCodes.com, Copyright © 2017 |
| Pages | 1 |
| File size | 0.2 MB |
| Format | |
| Language | English |
SPN 677 FMI 3 diagnostic overview
This Detroit sheet covers an engine starter relay shorted to a high source. The ignition must be off for at least 30 seconds first. The technician disconnects the Motor Control Module (MCM) 21-pin connector, turns the ignition on, and measures the voltage between pin 12 of the MCM 21-pin connector and ground. If voltage is present, the repair is to fix the short to power on pin 12 using the OEM wiring diagram; if no voltage is present, the starter relay is replaced.
Document table of contents
- Fault code identification
- Ignition-off notice (30 seconds)
- MCM 21-pin voltage check on pin 12
- Repair or starter relay replacement
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 a short-to-power condition on the engine starter relay circuit at the Motor Control Module 21-pin connector. For the OEM wiring schematics referenced in this procedure, see the official Detroit engine manufacturer site.
Who needs the SPN 677 FMI 3 manual
Workshop technicians and fleet owners using the diesel diagnostic tool to read Detroit fault codes and test the engine starter relay 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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