The existing research on multi-component systems mostly assumes that the faults between components are independent and ignores their practical correlation, which will inevitably affect the calculation of system warranty cost and warranty availability. In order to quantitatively analyze the impact of fault independence and fault correlation between components on the minimum two-dimensional extended warranty (EW) cost-availability ratio of the system, this paper establishes a two-dimensional EW cost model and availability model for multi-component systems considering fault correlation based on incomplete periodic preventive maintenance (PM), and forms a warranty cost-availability ratio model accordingly. Subsequently, the artificial bee colony (ABC) intelligent optimization algorithm was introduced to solve the model, and a case study was conducted on the transmission system of a certain new energy vehicle. Through numerical comparison, it was found that considering fault correlation compared to the assumption of fault independence would increase the warranty cost-availability ratio of the system by 20%, providing more practical warranty references for users and manufacturers, and verifying the superiority of the model. Finally, a sensitivity analysis was conducted on the model to guide its more effective implementation and application.