What causes a SPN 7378 code?

SPN 7378 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 7378 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 7378 active.

How do I fix SPN 7378?

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 7378

Cummins fault code 7378

What it means

Aftertreatment 1 Diesel Exhaust Fluid Dosing Unit Heater - Voltage Below Normal, or Shorted to Low Source. This indicates an electrical failure in the heating element internal to the DEF injector (doser).