FMI 31 — Condition exists / not available
A general 'this condition is present' flag, or the failure mode is not available. Many OEMs use it for status-type faults such as derates or inducements.
What it typically points to
Check what the SPN itself describes; the FMI simply says the condition is active.
Codes with FMI 31
- SPN 1569 FMI 31Engine Protection Torque Derate