What causes a SPN 2556 code?

SPN 2556 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 2556 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2556 active.

How do I fix SPN 2556?

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

Log in Sign up

J1939 SPN

SPN 2556

J1939 SPN 2556 — Aftertreatment/Emissions parameter

What it means

Aftertreatment Exhaust Temperature sensor 1 (Pre-DOC) has erratic voltage or data.

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free