Grove Sunlight Sensor Si1145/Si1151 has only values 0

I have purchased a Grove Sunlight Sensor Si1145 which uses Si1151. Cloned the demo project Seeed_Python_SI114x. In seeed_si114x.py I changed the code:

SI114X_ADDR = 0x60 to
#SI114X_ADDR = 0x60
SI114X_ADDR = 0x53

if self._ReadByte(SI114X_PART_ID) != 0X45: to
if self._ReadByte(SI114X_PART_ID) != 0X45 and self._ReadByte(SI114X_PART_ID) != 0X51:

to get the code running the desired way on a RaspBerry 4 B. But now all values of the sensor show 0. Might the sensor defect? Or has the code to be changed?