What causes a SPN 2042 code?

SPN 2042 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 2042 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2042 active.

How do I fix SPN 2042?

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 2042

SPN 2042 SCR Aftertreatment Reagent Tank Level Signal

What it means

This fault indicates an issue with the Diesel Exhaust Fluid (DEF) level sensor signal, suggesting the data is erratic or the tank level is not correlating with expected values.