What causes a SPN 4949 code?

SPN 4949 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 4949 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4949 active.

How do I fix SPN 4949?

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 4949

Cummins fault code 4949

What it means

VGT Actuator - Abnormal Update Rate. The Engine Control Module (ECM) has lost communication with the Variable Geometry Turbocharger (VGT) actuator via the J1939 data link.