FMI 31 — Condition exists

A catch-all: the named condition is present. It carries no failure-mode information, so the SPN is doing all the work.

Start free J1939 (CAN) → canonical

Diagnosis

When you hit this

Status-style DTCs where the SPN describes a state rather than a measurement.
Manufacturer-specific conditions that do not map to a standard failure mode.

Resolution

How to fix it

Go straight to the SPN
FMI 31 tells you nothing. Look up the SPN in the manufacturer's fault code list.
Expect proprietary meanings
Many FMI 31 codes are vendor-defined and need the OEM's service documentation.

Normalization

What Forge does about it

This code is reported by the device itself, so it survives normalization as data. Forge maps the vendor's fault register into the canonical fields alarm_code and alarm_description (and alarm_severity where the vendor supplies one), so an agent reads the same three fields whether the fault came from a Haas, a SINUMERIK, or a Cat engine. Forge does not clear the fault — that is the controller's job.