Automotive vehicles are becoming increasingly dependent on electric power, and this trend will accelerate. The health of the vehicular electric power generation and storage (EPGS) system is crucial to enhance vehicle safety, fuel economy, and reliability. In this paper, a fault detection and isolation method is presented for the automotive EPGS system, focusing on alternator related faults. Parity relations and structured residuals are designed using principal component analysis techniques. Real-time implementation and validation of the diagnostic algorithm have been successfully conducted by utilizing an automotive EPGS system test bench.