Code UI_a077 was reported by the “User interface” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The application layer of the touchscreen. Most codes from here are everyday notices the car shows the driver — an open frunk, a door left ajar, a status message about some feature. They are not hardware faults.
The most common type. The car logged the event and may have shown it on the screen. The range is wide — from something trivial that clears itself to something that needs attention.
This is how the fault is named inside the car's firmware. For codes without a description it is the most precise clue there is — the name itself says what the event is about.
The text below comes from Tesla's technical documentation. We leave it in the original English so that translation cannot shift its meaning.
The A2B microphone channels are in a swapped state
The device is in the swapped channel state if any of the first three channels are zero and any of the other channels are non zero
Microphone channels unswapped and correctly aligned
Microphone may be inoperative. Its audio stream will be restarted
Modem has stopped communicating.
The modem has stopped communicating
Ecall microphone is disconnected
ICE/BMP fails to detect or initialize the microphone and/or associated components
ICE/BMP detects and initializes the microphone and associated components
Audiod IO thread blocked, audiod restarted
ALSA IO function took longer than 10s (should be under 4ms), so audiod was restarted
Audiod was restarted, could result in audio artifact
The connection manager detected a problem with Wi-Fi and requested a reset
Wi-Fi connectivity may be unavailable
Successive modem power ON failures
The USB hub is not enumerating
The USB hub is not enumerating, it may be broken or disconnected.
USB hub may be broken or disconnected
Copy it exactly, letter and number included. Photographing the screen is safest — codes often differ by a single digit, and mixing them up leads somewhere else entirely.
Some codes clear after a screen restart or after the car sits locked for a few hours. If the code does not come back, it was usually a one-off glitch.
A one-off entry and a code that appears after every drive are two different things. It helps a service centre enormously if you know exactly when it shows up.
With airbags, brakes, steering and high voltage there is no point waiting it out. With the other groups you can watch and see whether the code returns at all.
Error codes are only part of the picture. For cars on TesList you also see battery health pulled straight from the vehicle, plus a price calculator that works out from current listings what a given car is actually worth today.