Code GTW_w157 was reported by the “Gateway” controller in the car. The letter “w” in the middle places it among entries of the warning type.
The Gateway — the hub through which the car's controllers talk to each other, and the route software updates take. Codes from here often mean some controller has gone quiet on the bus; the real fault is usually in that controller, not the gateway.
The car is flagging that something is not right. Driving is usually still possible, but some function may be limited.
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.
There has been an issue in providing support to the low voltage (LV) bus, and the voltage has dropped below the target. This can be caused by:Wiring issues between the DCDC and rest of vehicle on LV harness (B+ or ground).Loose 12V battery positive or negative connections at either end of the harness.No LV support provided due to low Battery Management System (BMS) State of Charge (SOC).No LV support provided due to BMS issues.No LV support provided due to DCDC issues.No LV support provided due to E-fuse DCDC fuse tripped.DCDC is not enabled by the BMS or E-fuse.Controller area network (CAN) bus issues with PT or BDY.
This alert does not mean the 12V battery is bad. It means the vehicle is not adequately supporting the 12V battery and LV system.
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.