U0300 on Mazda vehicles

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.

Bulletins and campaigns Mazda filed with NHTSA whose summary names U0300. Quote the document number at the service desk — it is a diagnosis the maker has already written down.

• SA-003/22 Service bulletin
  2022-01-21 · Equipment
• Some vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction) after a BCM replacement or MDARS BCM software update (NOT with BCM update for SSPC5 or 4621B using MDRT) and the DTC cannot be erased. This is caused by a BCM-VCM software error. Mazda is aware of the issue and is working on a resolution. If there is an issue with this concern, Mazda recommends putting customer i
• SA-003-22a Service bulletin
  2022-02-04 · Electrical System
• Some vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction) after a BCM replacement or MDARS BCM software update (NOT with BCM update for SSPC5 or 4621B using MDRT) and the DTC cannot be erased. This is caused by a BCM-VCM software error. Mazda is aware of the issue and is working on a resolution. If there is an issue with this concern, contact Hotline for newest repair i
• SA-003-22b Service bulletin
  2022-02-09 · Electrical System
• CX-30. Mazda3: Prior to February 8, 2022, some vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction) and cannot be erased after a BCM replacement or MDARS BCM software update (NOT with BCM update for SSPC5 or 4621B using MDRT). This is caused by a BCM-VCM software error. Customers having this concern should have their vehicle repaired using the following repair procedure
• SA-003-22c Service bulletin
  2022-03-04 · Electrical System — Adas — Hud — Software
• Mazda3 and CX-30: Prior to February 8, 2022, some vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction) and cannot be erased after a BCM replacement or MDARS BCM software update (NOT with BCM update for SSPC5 or 4621B using MDRT). This is caused by a BCM-VCM software error. MX-30: Some MX-30 vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction
• SA-003-22d Service bulletin
  2022-03-11 · Electrical System — Software
• Mazda3 and CX-30: Prior to February 8, 2022, some vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction) and cannot be erased after a BCM replacement or MDARS BCM software update (NOT with BCM update for SSPC5 or 4621B using MDRT). This is caused by a BCM-VCM software error. MX-30: Some MX-30 vehicles may store DTC U0300:57 (Body control module (BCM) internal malfunction

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.