Code IBST_d108 was reported by the “Brake booster (iBooster)” controller in the car. The letter “d” in the middle places it among entries of the diagnostic entry type.
The electromechanical brake booster. It provides pedal assistance and works together with regenerative braking. These codes show up as a harder pedal and a message about reduced braking — the brakes still work mechanically, but need much more force.
A service record that is not shown to the driver. Only a technician sees it in diagnostics.
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 Serial Peripheral Interface (SPI) failure detection unit of each Application-specific integrated circuit (ASIC) (system ASIC / Valve ASIC / RFP ASIC) is tested for correct detection and response of parity, address, and clock failures on the SPI protocol.
The initial test of the SPI failure detection functionality in any ASIC inside the electronic control unit (ECU) failed (SPI address Read / Write test, SPI parity test, and SPI clock test). This could indicate that wrong data is being sent to the ASIC or there is a defect in the SPI transceiver or the SPI lines.
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.