What causes a P170D code?

P170D 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 P170D code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P170D 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

P170D

UNSRD NOx sensor up model dynamic response negative fault

What it means

Upstream NOx sensor dynamic response fault (slow response). The ECM has determined the sensor is not reacting quickly enough to changes in exhaust gas composition.