KarlaSvalina:
It is not problem with that. I try to test mpu6050 and led on pin 13 is always on. This test example is from electronoobs page. In code there isn't command that turn led 13 on.
Pin13 is also the SCK pin, so when SPI is in use, it will flicker when SPI is actively transferring data, and stay on (or off depending on the SPI mode used) when not transferring data.