Remote fault diagnosis circuit, detection method and multi-split air conditioning unit

The invention discloses a remote fault diagnosis circuit, and the circuit comprises a rectification filtering module, an MCU, a communication module and a power detection module, wherein the rectification filtering module, the MCU and the communication module are connected between an AC power supply and a communication bus, and the power detection module is connected with the AC power supply and the MCU; the rectifying and filtering module is used for rectifying, filtering and storing energy and supplying power to the MCU; the power detection module is used for detecting whether the AC power supply is powered off or not and sending a power-off signal to the MCU; the MCU is used for diagnosing faults of a multi-split air conditioner, distinguishing whether the AC power supply is powered offor not and sending out fault codes. The communication module is used for transmitting a fault code to the communication bus. According to the invention, the problem that a current multi-split air conditioner cannot distingui