What does SPN 515 FMI 0 (515/0) mean?

Engine's Desired Operating Speed: data above normal range (most severe level).

What does SPN 515 FMI 15 (515/15) mean?

Engine's Desired Operating Speed: above normal — low severity.

Do not drive. Stop as soon as it’s safe to do so — don’t keep going.

Do not driveTo the nearest safe stop

J1939 code SPN 515. Below — how the fault is worded at the factory by SITRAK, and what the second half of the code (FMI) means in the standard.

FMI 0	Engine speed reaches ignition cutoff limit
FMI 15	Engine speed exceeds maximum governed speed
FMI 16	Engine speed reaches fuel cutoff limit
FMI 31	Engine speed exceeds maximum allowable value

SPN 515 FMI 0515/0 · 515.0	data above normal range (most severe level)
SPN 515 FMI 15515/15 · 515.15	above normal — low severity
SPN 515 FMI 16515/16 · 515.16	above normal — moderate severity
SPN 515 FMI 31515/31 · 515.31	condition exists (see manufacturer description)

Do not drive. Stop as soon as it’s safe to do so — don’t keep going.

Time you have: To the nearest safe stop

The code is flagged critical: the manufacturer considers it unsafe to keep driving without checking.

This code alone cannot say what will fail next, so stop at the first safe opportunity and look at it on the spot.

That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.

Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.