To provide a physical quantity detector diagnosing abnormality more reliably, to provide a method of controlling the physical quantity detector, and to provide a system and a method for diagnosing abnormality.

An angular velocity detector 1 (one example of the physical quantity detectors) includes: a gyrosensor element 100 (one example of physical quantity detection elements) for generating a detection signal corresponding to the magnitude of angular velocity (one example of physical quantities) and a leakage signal of vibration based on a drive signal (square wave voltage signal 22) in a detection electrode; a drive circuit 20 for generating a drive signal; a synchronous detection circuit 350 for performing synchronous detection to a signal 36 to be detected including a detection signal and a leakage signal, based on a detection signal 34 in synchronization with the drive signal; and a phase change circuit 352 for changing relative timing of at least one of rising and falling of the detection signal 34 to the signal 36 to be detected so that at least one portion of the leakage signal is outputted by synchronous detection, based on a control signal 64.