What causes a P0321 code?

P0321 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 P0321 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0321 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

P0321

Ignition/Distributor Engine Speed Input Range/Performance

What it means

The Engine Control Module (ECM) has detected an irrational or out-of-range signal from the crankshaft position sensor (CKP) or camshaft position sensor (CMP), indicating a synchronization issue.