What causes a SPN 405 code?

SPN 405 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 405 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 405 active.

How do I fix SPN 405?

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 405

J1939 SPN 405 — Fuel/Air parameter

What it means

This is a generic J1939 parameter code indicating that the control module has detected an abnormality in the ratio of fuel to air being delivered to the engine, or the data describing that ratio is invalid.