What causes a SPN 955 code?

SPN 955 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a SPN 955 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 955 active.

How do I fix SPN 955?

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

J1939 SPN

SPN 955

J1939 SPN 955 — Engine Management parameter

What it means

SPN 955 specifically identifies the Water-In-Fuel (WIF) indicator circuit or sensor status. It indicates that the fuel-water separator has detected excessive water or there is a circuit fault.