What causes a SPN 770 code?

SPN 770 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 770 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 770 active.

How do I fix SPN 770?

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 770

J1939 SPN 770 — Engine Management parameter

What it means

SPN 770 indicates an electrical fault (short to ground, short to battery, or open circuit) in the Selective Catalytic Reduction (SCR) Line 2 heating circuit. This heating element is required to prevent Diesel Exhaust Fluid (DEF) from freezing in colder temperatures.