SPN 98 FMI 1 — Engine oil level low

SPN 98 identifies the parameter the control module is monitoring — engine oil level low. FMI 1 is the failure mode the module logged against it. Both numbers matter: the same SPN with a different FMI is a different repair.

No immediate derate, but the clock is running.

• Oil consumption or leak
• Overdue oil service
• Faulty level sensor

• Check the dipstick on level ground
• Look under the truck for a fresh leak
• Add oil to the full mark

Work the list in order and record the readings. Confirm the fault with live data before any part is ordered — a code names a circuit, never a failed component.

Generally safe to finish the trip

Add oil and you are good to drive home. Recheck every fuel stop.

• Replacing the sensor named in the SPN before checking its wiring, connector and ground.
• Clearing the code and handing the truck back without reproducing the operating condition that set it.
• Reading one code out of a set instead of finding which fault occurred first.

Get a shop involved when the fault comes with a red lamp or a shutdown timer, when the checks above all pass and the code returns, or when the repair needs an aftertreatment service tool, a forced regen, or engine internals. Nothing on this page is a substitute for OEM service literature or a qualified technician on the truck.

Enter this code in Blue Collar AI diagnostic support with the engine and the symptoms and you get the test sequence in order, per-truck history so repeat faults are visible, and a printable work order. Aftertreatment codes are covered in depth in the Aftertreatment Mastermind training. It is all in Truck Commander at $14.99 a month.