What causes a SPN 3749 code?

SPN 3749 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 3749 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3749 active.

How do I fix SPN 3749?

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 3749

J1939 SPN 3749 — Body/Chassis parameter

What it means

Aftertreatment SCR Inducement Catalyst Gas Temperature Sensor - Data erratic, intermittent, or incorrect (Note: In many J1939 contexts, 3749 specifically refers to a mismatch or configuration error regarding Body/Chassis interface data).