For digital proportional-integral-derivative control systems with unknown dynamics, the data-driven output-feedback fault-tolerant control (FTC) problem is studied in this paper. In a framework of active FTC, the issue of online recursive identification of the residual generator, the state observer, and the observability canonical form of the plant under consideration is addressed; the problem of reconfiguration of the data-driven fault-tolerant compensation controller with L-2-gain properties is also dealt with by means of the above-obtained results, the prefilter and the Riccati equation related to H-infinity control so as to accommodate faults and ensure tracking performance. The resulting fault-tolerant compensation control scheme is designed based on the closed-loop systems, and therefore has more practical significance than the existing FTC methodologies developed in terms of the open-loop systems. Finally, the effectiveness of the proposed FTC approach is validated by the speed control experiment on a dc motor.