If the bulb is normal, the lights inside the bulb have not broken, and it is necessary to remove the bulb after comparison, see if the bulb specification is consistent (general bulb distinguished unit and double tail, divided into high-grab and low-grab) replacement bulb There will be such a fault in the specification, and the quality of the bulb is not closed, and the brightness of the light will be insufficient, and the above fault will occur.
The light-transmitting control unit software version is too low, or the right light-related line is faulty, and it is necessary to further use the multimeter for measurement.
After the measurement, if the relevant line voltage is normal, it is necessary to check that the relay of the bulb and the fuse is damaged, and the test light can be checked, or the fuse is performed.