Circuit/System Description
WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.
The B20 Brake Fluid Level Sensor is a normally open switch that closes when the brake fluid is below the minimum level. The switch is magnetically actuated by a float. The K160 Brake System Control Module monitors the switch on signal circuit 333 and the switch receives a constant ground on ground circuit 751.