B12C5: owner reports and bulletins

Body. We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

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What owners report to NHTSA

12 complaints filed with NHTSA mention B12C5, 12 of them since 2015, across 4 different models. The component owners most often filed it under: electrical system.

Most-reported models

VehicleComplaintsModel years reported
HONDA HR-V42016, 2017
HONDA PILOT42016, 2017
HONDA FIT32015

Manufacturer service bulletins that name B12C5

8 technical service bulletins and manufacturer communications filed with NHTSA mention B12C5, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • HONDA HR-V (2016, 2017, 2018), bulletin 10184329: Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. …
  • HONDA FIT (2015, 2016, 2017), bulletin 10184317: Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. …
  • HONDA RIDGELINE (2017, 2016), bulletin 10184330: Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. …
  • ACURA NSX (2017), bulletin 10184335: Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. …

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.