What causes a P0422 code?

P0422 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 P0422 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0422 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

P0422

Main Catalyst Efficiency Below Threshold (Bank 1)

What it means

The Engine Control Module (ECM) has detected that the catalytic converter's ability to store oxygen and reduce tailpipe emissions has fallen below a predetermined efficiency level.