What causes a P170C code?

P170C 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 P170C code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P170C 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

P170C

UNSRD NOx sensor overrun diagnostic

What it means

The Engine Control Module (ECM) detected that the Upstream NOx sensor reported values outside of the expected range during a zero-fuel (overrun/deceleration) event.