What causes a SPN 668 code?

SPN 668 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 668 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 668 active.

How do I fix SPN 668?

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 668

J1939 SPN 668 — Engine Management parameter

What it means

Transmission Shift Lever Error. The Engine Control Module (ECM) is receiving invalid data or has lost communication with the transmission gear selector via the J1939 data link.