The taillight bulb is damaged, and the brake fluid cup is divided into upper and lower lines. When the brake fluid inside is lower than the off-line level, this phenomenon will be sensed by the sensor next to the oil cup and reflected by the brake light on the instrument panel. If the brake fluid decreases quickly, it means that the brake system is leaking: just replace the light bulb.
It takes about two or three hundred yuan to replace the taillights of Wuling Rongyao Xiaoka in the 4s shop. Taillights are not particularly expensive, but the working hours are relatively high. They all choose to replace it outside, which is about tens of yuan. If you change it yourself, I'm afraid you don't have any tools.