What causes a SPN 7812 code?

SPN 7812 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 7812 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 7812 active.

How do I fix SPN 7812?

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 7812

Cummins fault code 7812

What it means

Unswitched Battery Supply - Voltage Below Normal, or Shorted to Low Source. The ECM has detected a loss of permanent battery power on its main supply pins.