What causes a SPN 6748 code?

SPN 6748 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 6748 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6748 active.

How do I fix SPN 6748?

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 6748

Cummins fault code 6748

What it means

Aftertreatment 1 Outlet NOx Sensor Heater - Voltage Below Normal or Shorted to Low Source. This indicates the ECM detects the heater circuit for the outlet (downstream) NOx sensor is not achieving the required current or is shorted.