What causes a SPN 2056 code?

SPN 2056 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 2056 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2056 active.

How do I fix SPN 2056?

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 2056

SPN 2056 - Diesel Exhaust Fluid (DEF) Tank Heater Control Circuit Fault

What it means

The Engine Control Module (ECM) has detected an open circuit, short to ground, or short to voltage in the control circuit for the Diesel Exhaust Fluid (DEF) tank heater valve.