What causes a SPN 685 code?

SPN 685 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 685 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 685 active.

How do I fix SPN 685?

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 685

J1939 SPN 685 — Engine Management parameter

What it means

SPN 685 indicates an 'Engine Management Parameter' error, signifying that the control system has detected invalid or missing configuration data required for engine operation.