What causes a SPN 6377 code?

SPN 6377 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 6377 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6377 active.

How do I fix SPN 6377?

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 6377

Cummins fault code 6377

What it means

Variable Geometry Turbocharger (VGT) Actuator - Loss of Communication. This code indicates the ECM has lost the CAN data link connection with the smart actuator on the turbocharger.