What causes a SPN 6685 code?

SPN 6685 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 6685 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6685 active.

How do I fix SPN 6685?

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 6685

Cummins fault code 6685

What it means

Particulate Matter (PM) Sensor - Abnormal Update Rate. This indicates the Aftertreatment PM Sensor is unable to communicate with the Engine Control Module (ECM) or is sending invalid data.