What causes a P1848 code?

P1848 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 P1848 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1848 active.

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

OBD-II

P1848

Upstream NOx sensor heater FMI monitor fault

What it means

The Engine Control Module (ECM) has detected that the heating element in the upstream NOx sensor (located before the SCR/DPF) is not functioning. The sensor must reach a specific operating temperature to provide accurate nitrogen oxide readings.