Detailed guide for SPN 677 FMI 2
Back to top ↑What SPN 677 FMI 2 means
SPN 677 FMI 2 is documented by Detroit as a starter switch inconsistent fault.
The fault sets when the starter ignition status reported by the Common Powertrain Controller and Motor Control Module do not agree.
What you may notice
The check-engine light may illuminate.
On the documented Detroit application, there is no direct engine reaction, although the underlying starter or ignition-signal problem may affect starting behavior depending on the cause.
What to check first
Check for other starter, ignition or controller communication faults.
Inspect starter relay and starter-signal wiring between the applicable controllers.
Use the OEM diagnostic tool to compare starter status reported by the CPC and MCM during engine start.
Important
This fault identifies inconsistent starter-status information. It does not automatically mean the starter motor itself has failed.
Follow the wiring diagram and OEM diagnostic procedure before replacing the starter or controller.
Mechanic community notes for SPN 677 FMI 2
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