What causes a U0321 code?

U0321 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 U0321 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with U0321 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

Log in Sign up

OBD-II

U0321

Suspension Control Module Software Incompatibility

What it means

Active suspension or air ride software is mismatched, which can lead to poor ride quality or incorrect ride height.

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free