What causes a P2221 code?

P2221 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 P2221 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P2221 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

P2221

NOx Sensor Heater Control Circuit Range/Performance Bank 1 Sensor 2

What it means

The Engine Control Module (ECM) detects an issue with the heating element circuit of the downstream nitrogen oxide sensor, preventing it from reaching optimal operating temperature.