Examples of a system and method for temperature measurements and identifying a location of temperature measurement system failure are disclosed. The system comprises a light source and a detector mounted to a single substrate. When the system is in a temperature measuring mode, a driving circuit is providing a drive current pulse to the light source and the receiving circuit is receiving an emitted light from the sensor. If an amplitude of the emitted light is within a predetermined threshold, a failure in the sensor or an optical path is identified. When the system is in a monitoring mode, a continues drive current is provided to the light source so that the receiving circuit receives the return light and if the amplitude of the return light subtracted by the amplitude of the emitted light is within a predetermined threshold, a failure of the light source is identified.