Code IBST_d100 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 error pin counter in the system Instrument Cluster (IC) does not increment error pin events or decouple bits that are not reset by the system IC. The failsafe logic test pulls the error pin in order to test the error pin event counter within the system chip. To prevent an electrical shutdown, which would disturb communication, during the provoked error pin event, the electrical decouple bit is set. It is also tested that the decouple bit gets reset.
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.