What causes a P1842 code?

P1842 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 P1842 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1842 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

P1842

Upstream NOx sensor AT1IGC2 low rate fault

What it means

The Aftertreatment Inlet (Upstream) NOx sensor is responding slower than the ECM expects during a calibration or monitoring event, indicating the sensor is degraded or failing.