Glossary
SPN: Suspect Parameter Number
The number that identifies the component, circuit, or parameter a controller is watching.
Definition updated 2026-10-25 · Report a correction
What an SPN is
SPN stands for Suspect Parameter Number. In the SPN/FMI format used by many controllers, the SPN identifies the parameter being watched: a sensor reading, a circuit, a message, or a calculated value. The FMI then says how that parameter failed. A code such as SPN 110 / FMI 3 therefore points to one parameter (engine coolant temperature) and one failure mode (voltage above normal or shorted high), not to a single part number.
SPNs come from two broad worlds. Some are common industry numbers, such as SPN 110 for engine coolant temperature or SPN 190 for engine speed. Others are manufacturer-specific, such as the 520xxx numbers used in many Polaris tables. Both appear in this archive. The number is an identifier, not a part number, and the same SPN can be paired with several FMIs.
How the archive groups SPNs
The archive keeps one record per observed SPN/FMI key. A key can carry several printed labels because different manuals describe the same parameter in different words. For example, SPN 110 / FMI 3 appears as “Engine Coolant Temperature - Voltage Above Normal, Or Shorted To High Source” in one table and as a shorter “Engine Temperature Sensor - Voltage Too High” in another. The labels are kept together so a search by either wording reaches the same key.
The code index lists every key, the number of model records that publish it, and a link to a page where it appears. The decoder accepts an SPN and FMI directly, which is faster when both numbers are already known.
Why the same SPN can look different
An SPN alone is incomplete. The same number can be reused in different controller families, and a manufacturer-specific SPN has no meaning outside the source that defines it. The model year, the controller, and the manual table all matter. The archive therefore publishes the OEM label and the source record with each entry instead of translating an SPN into a repair instruction.
The current archive carries 322 distinct SPNs across 16,043 entries that include an FMI value. That count is a property of the collected manuals, not a claim about every machine or every model year.