What causes a SPN 4344 code?

SPN 4344 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 4344 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4344 active.

How do I fix SPN 4344?

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.

J1939 SPN

SPN 4344

Detroit DD13/DD15/DD16 SPN 4344

What it means

Aftertreatment 1 SCR Intake Temperature - Data Valid But Below Normal Operating Range - Least Severe Level. This code indicates that the Selective Catalytic Reduction (SCR) system is not reaching the required temperature for efficient NOx conversion or the dosing system is struggling to maintain efficiency.