What causes a SPN 440 code?

SPN 440 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 440 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 440 active.

How do I fix SPN 440?

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 440

J1939 SPN 440 — Fuel/Air parameter

What it means

SPN 440 is a generic J1939 parameter for Fuel/Air related pressure. In most heavy-duty applications, it specifically monitors the Fuel Delivery Pressure, flagging values that are out of range (High, Low, or Erratic).