What causes a P1849 code?

P1849 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 P1849 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1849 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

P1849

Upstream NOx sensor heater response monitor fault

What it means

The Engine Control Unit (ECU) has detected that the Upstream (Inlet) NOx sensor's internal heater is not responding correctly or fast enough to reach its required operating temperature of approximately 1400°F (760°C).