What causes a SPN 349 code?

SPN 349 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 349 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 349 active.

How do I fix SPN 349?

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 349

J1939 SPN 349 — Fuel/Air parameter

What it means

SPN 349 typically monitors the Ambient Air Pressure or related Fuel/Air ratio parameters. It indicates the ECM is receiving a signal that is out of range or inconsistent with other sensor readings like boost pressure.