Glossary
FMI: Failure Mode Identifier
The number that describes how a monitored parameter failed.
Definition updated 2026-10-25 · Report a correction
What an FMI is
FMI stands for Failure Mode Identifier. It is the second number in an SPN/FMI pair. The SPN identifies the parameter; the FMI describes how that parameter failed. In a printed pair such as SPN 110 / FMI 3, the 3 is the FMI. It is not a severity score on its own, and it is not a part number.
The common SAE-style table defines values 0 through 31. Many values describe a circuit condition: voltage above or below normal, current below or above normal, an open circuit, or a ground. Others describe a signal problem, a mechanical problem, a calibration problem, or a condition that simply exists. The FMI reference reproduces the common table and the archive counts for each value.
The common value families
FMI 3 and 4 are the voltage pair: above normal or shorted high, and below normal or shorted low. FMI 5 and 6 are the current pair: below normal or open circuit, and above normal or grounded circuit. FMI 7 is a mechanical system that is not responding or is out of adjustment. FMI 8, 9, and 10 cover abnormal frequency, update rate, and rate of change. FMI 11 means the root cause is not known, FMI 12 means a bad intelligent device or component, and FMI 13 means out of calibration.
FMI 14 carries special instructions, FMI 15 through 18 carry severity-qualified high and low readings, FMI 19 covers received network data in error, and FMI 20 and 21 cover data that drifted high or low. FMI 31 says a condition exists. Values 22 through 30 are reserved in the common table. Values 36 and 37 are outside the common range and appear in this archive only because a source printed them.
What the archive shows
The archive currently has 16,043 entries with an FMI value, collapsing to 746 distinct SPN/FMI pairs. The most frequent values are FMI 3, 4, 5, and 31. That ranking reflects the manuals collected here, not the failure rate of any machine. The FMI reference lists every observed value with its entry, SPN, and model counts, plus a representative OEM label.
An FMI can be used more narrowly by a manufacturer. FMI 31 is the clearest example: the common table says “condition exists,” while the OEM label may name a protection, a derate, or a module state. The printed label is the useful description for a specific table.
What an FMI does not tell you
An FMI does not identify a failed part, a repair, or a safe operating limit. A voltage-high FMI can come from a sensor circuit, a connector, a supply, or the controller’s interpretation. The archive keeps the OEM label and the source record so a reader can compare the exact wording instead of treating the generic FMI as a diagnosis.
Use the model-year page for the table that matches a machine, and use the label-variance reference when the same FMI appears under several descriptions.