P0321: owner reports and bulletins

Powertrain (generic, all makes). We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

Got P0321 on your scanner? Tell the mechanic your year, make, model and any symptoms and you'll get the likely cause and what to check first. Ask about this code.

What owners report to NHTSA

No consumer complaints filed with NHTSA mention P0321. That usually means it's rare, or owners don't quote the code when they file.

Manufacturer service bulletins that name P0321

1 technical service bulletins and manufacturer communications filed with NHTSA mention P0321, from 1 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • AUDI RS 3 (2023, 2024), bulletin 10247196: This bulletin provides information for when the engine starts poorly, emission warning lamp is illuminated - engine speed sensor G28, P0321.

Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.