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U1A4B on the 2021 Mazda Mazda2

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

This code is specific to a manufacturer and is not described here. Its meaning is in the manufacturer's service information.

Bulletins for this model year that name U1A4B
09-041-222022-11-04. Service bulletin. 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 may be found if the right-side BSM module is replaced alone: * BSM aiming fails * "BSM OFF" indicator ON * Center Display warning message * BSM failsafe (No operation) * DTC U3000:54 stored in memory * DTC U1A4B:54 stored in memory (CX-3, MX-5 only)

1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.