What causes a SPN 1858 code?

SPN 1858 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 1858 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 1858 active.

How do I fix SPN 1858?

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 1858

SPN 1858 Driveline Axle Differential Separator Status

What it means

This fault code monitors the status or electrical integrity of the driveline differential lock or separator mechanism used to engage or disengage axle power.