Abstract: In an automotive radio system an amplifier is capable of detecting speaker faults. A fault signal from the amplifier is received by a microprocessor which sends a fault message to a radio display and/or stores fault data which can be accessed via a serial data link by a diagnostic tool. One embodiment of the amplifier has an output pin for outputting distortion signal, and that pin is used when distortion is not likely to also output a fault signal which reveals the presence of a fault. Another embodiment of the amplifier has a data storage register which receives data on the type of fault and the affected channel, and a data bus to send the data to the microprocessor.