The well-functioning of disc-pad brake subsystems concerns the safe operation of both automobiles and trains. However, there is a lack of effective constant condition monitoring methods for the vital disc-pad brake pairs in such brake subsystems of driving vehicles. Therefore, we propose a brake pair misalignment detection scheme based on a battery-free electromagnetic-based gap sensor, to deal with several common brake pair misalignments including distance changes, translational deviations, and rotary deflections. The alternating-polarity magnet array in the proposed sensor on the brake disc generates a unique distribution of the effective magnetic flux density within a relatively moving microfabricated planar coil sheet along with the brake pad, which is sensitive to the varied gap if misalignments occur between the disc-pad brake pair. Thus, discriminative voltage performance is induced by the inductive planar coils in response to different misalignment types and degrees. Comprehensive finite element simulation analysis and experiments are conducted to elaborate the misalignment detection capability of the proposed sensor. The proposed scheme has the potential to enhance the self-perception of intelligent vehicle systems, without adding the power consumption burden due to the battery-free nature of the electromagnetic-based sensor.