U1A4B on Mazda vehicles
U1A4B is named on 15 Mazda model years (2016–2024): 36 manufacturer filings and 0 owner reports in NHTSA’s files, across MX-5, CX-3.
Which Mazda model years name U1A4B
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2016 Mazda MX-5 | Electrical System | 7 | — |
| 2016 Mazda CX-3 | Electrical System | 4 | — |
| 2017 Mazda CX-3 | Electrical System | 3 | — |
| 2022 Mazda MX-5 | Electrical System | 2 | — |
| 2021 Mazda CX-3 | Electrical System | 2 | — |
| 2021 Mazda MX-5 | Electrical System | 2 | — |
| 2020 Mazda CX-3 | Electrical System | 2 | — |
| 2020 Mazda MX-5 | Electrical System | 2 | — |
| 2019 Mazda CX-3 | Electrical System | 2 | — |
| 2019 Mazda MX-5 | Electrical System | 2 | — |
| 2018 Mazda CX-3 | Electrical System | 2 | — |
| 2018 Mazda MX-5 | Electrical System | 2 | — |
| 2017 Mazda MX-5 | Electrical System | 2 | — |
| 2024 Mazda MX-5 | Electrical System | 1 | — |
| 2023 Mazda MX-5 | Electrical System | 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 U1A4B
Source: NHTSA manufacturer communicationsBulletins and campaigns Mazda filed with NHTSA whose summary names U1A4B. Quote the document number at the service desk — it is a diagnosis the maker has already written down.
- 15-002/15 Service bulletin2015-12-10 · Electrical System
- BSM OFF INDICATOR ON WITH DTC U1A4B:97 OR U3000:97. SOME VEHICLES WITH BLIND SPOT MONITORING (BSM) MAY EXPERIENCE THE FOLLOWING CONDITIONS (SIMILAR TO WHEN THE BSM CONTROL MODULES DETECT DIRT ON REAR BUMPERS SURFACE): BSM TURNS "OFF" AND BSM OFF INDICATOR TURNS "ON" IN THE INSTRUMENT CLUSTER WHILE DRIVING; BSM WILL NOT TURN ON AGAIN DURING DRIVE CYCLE; AFTER CYCLING, IGNITION SWITCH OFF AND ON
- 15-002-15-3109 Service bulletin2015-12-09 · Lane Departure — Blind Spot Detection
- SOME VEHICLES WITH BLIND SPOT MONITORING (BSM) MAY EXPERIENCE THE FOLLOWING CONDITIONS (SIMILAR TO WHEN THE BSM CONTROL MODULES DETECT DIRT ON THE REAR BUMPER SURFACE): THE BSM TURNS OFF AND THE BSM OFF INDICATOR TURNS ON IN THE INSTRUMENT CLUSTER WHILE DRIVING THE BSM WILL NOT TURN ON AGAIN DURING THE DRIVE CYCLE AFTER CYCLING THE IGNITION SWITCH OFF AND ON AGAIN, THE BSM OPERATES NORMAL
- 15-001-17-3301a Service bulletin2017-09-01 · Electrical System — Software
- Some vehicles with Blind Spot Monitoring (BSM) may experience the following conditions (similar to when the BSM control modules detect dirt on the rear bumper surface): DTC U1A4B:97 - Radar sensor sensitivity temporarily decreases depending on various external and environmental factors (blind spot monitoring (BSM) control module (RH)), DTC U3000:97 - Radar sensor sensitivity temporarily decreases
- 09-017-19-3473 Service bulletin2019-03-28 · Equipment Adaptive/Mobility
- If the right-side Blind Spot Monitoring (BSM) control module is replaced for any reason, it is also necessary to replace the left-side BSM control module in order to complete the radar aiming procedure. If the right-side BSM control module is replaced alone, "Automatic Configuration" and "BSM Radar Aiming" cannot be completed due to a programming error in the module. Other possible symptoms that m
- 09-041-22 Service bulletin2022-10-11 · Electrical System
- If the right-side Blind Spot Monitoring (BSM) control module is replaced for any reason, it is also necessary to replace the left-side BSM control module in order to complete the radar aiming procedure. If the right-side BSM control module is replaced alone, "Automatic Configuration" and "BSM Radar Aiming" cannot be completed due to a programming error in the module. Other possible symptoms that
- 09-005-26 Service bulletin2026-01-13 · Electrical System
- If the right-side Blind Spot Monitoring (BSM) control module is replaced for any reason, it is also necessary to replace the left-side BSM control module in order to complete the radar aiming procedure. If the right-side BSM control module is replaced alone, "Automatic Configuration" and "BSM Radar Aiming" cannot be completed due to a programming error in the module. In most cases, if the left-sid
What U1A4B means
Source: SAE J2012 / OBD-IIU1A4B is a manufacturer-specific code: the second character is a 1, which under the OBD-II standard hands the definition to whoever built the vehicle. The same code can mean one thing on a Ford and something unrelated on a Hyundai. Any site that prints a single definition for it is guessing.
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 U1A4B a known problem on Mazda vehicles?
It is a documented one: NHTSA's files hold 36 manufacturer filings and 0 owner reports naming U1A4B on 15 Mazda model years (2016–2024). 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 U1A4B appear on most?
2016 MX-5 (7 documents), 2016 CX-3 (4 documents), 2017 CX-3 (3 documents).
Does U1A4B 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.