Honda Civic 2016–2019 — technical service bulletin
Bulletin A16040B · NHTSA communication 10160913 · issued May 31, 2019
Technical service bulletin
communication type
Electrical System
component
2016–2019
model years
4
vehicle entries
Official summary
Service Bulletin - The 12-pin connector cavity in the back of the audio unit/audio-navigation unit is intentionally empty. It's used as a service port for other markets, so never try plugging into it.
Vehicles covered
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.