What causes a SPN 857 code?

SPN 857 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 857 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 857 active.

How do I fix SPN 857?

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 857

J1939 SPN 857 — Engine Management parameter

What it means

SPN 857 is a generic J1939 parameter used to indicate a network communication issue specifically related to a sub-component managed by the Engine Management System. It often implies the ECM is not receiving expected data from an auxiliary engine device.