C0021 on Mazda vehicles
C0021 is named on 5 Mazda model years (2019–2021): 5 manufacturer filings and 0 owner reports in NHTSA’s files, across CX-30, Mazda3.
Which Mazda model years name C0021
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2021 Mazda CX-30 | Service Brakes | 1 | — |
| 2021 Mazda Mazda3 | Service Brakes | 1 | — |
| 2020 Mazda CX-30 | Service Brakes | 1 | — |
| 2020 Mazda Mazda3 | Service Brakes | 1 | — |
| 2019 Mazda Mazda3 | Service Brakes | 1 | — |
A model year is listed because the code is named in its own record — a bulletin filed against it, or an owner’s complaint about it — not because every one of these vehicles sets it. Counts are documents in NHTSA’s files, not failure rates.
Mazda filings that name C0021
Source: NHTSA manufacturer communicationsBulletins and campaigns Mazda filed with NHTSA whose summary names C0021. Quote the document number at the service desk — it is a diagnosis the maker has already written down.
- SA-044-21 Service bulletin2021-07-13 · Service Brakes, Hydraulic
- When switching to the maintenance mode, U3000:53 and the related DTCs are stored, but the DTCs will not be cleared automatically after finishing the maintenance mode. It is necessary to clear the DTCs completely after performing the brake system maintenance mode. DTC codes: U3000:53, C0021:52, U0415:68
What C0021 means
Source: SAE J2012 / OBD-IIC0021 sits in the generic range of the OBD-II standard, so it means the same thing on every vehicle sold in the United States — but WhichTrim does not carry a definition for it and will not invent one. What is on this page is the record: who named it and on what.
A stored code names the test that failed, never the part that caused it. The record above is what Mazda and its owners have filed about it; the code’s page across every make has the whole file.
Common questions
Source: NHTSA files and the OBD-II standardIs C0021 a known problem on Mazda vehicles?
It is a documented one: NHTSA's files hold 5 manufacturer filings and 0 owner reports naming C0021 on 5 Mazda model years (2019–2021). Whether it is a problem on one particular car is a diagnosis, not a count — but a bulletin that names the code on your model year is the place to start.
Which Mazda models does C0021 appear on most?
2021 CX-30 (1 document), 2020 CX-30 (1 document), 2021 Mazda3 (1 document).
Does C0021 on a Mazda mean it is recalled?
No. Recalls are filed by campaign and matched by VIN; no recall is triggered by a scan tool. Check the VIN at nhtsa.gov/recalls, or open the model year's page here for the campaigns filed against it.