We propose a subwavelength electromagnetic diode scheme in microwave waveguide systems by using an asymmetric photonic crystal (PC) cavity side-coupled with electromagnetically induced transparency like (EIT-like) metamaterials. We find that the composite PC-EIT configuration can generate tenfold Q-factor enlargements, with enhanced nonreciprocal electromagnetic (EM) localization simultaneously. Further study on the measured one-way responses exhibits excellent electromagnetic diode performance including 19.7 dB transmission contrast and 7 dBm operating power at working frequency 1.329 GHz. We emphasize that such high-contrast transmission and low-threshold diode actions are not at costs of greatly increasing volume and drastically decreasing transmission. Our findings may benefit the design of compact nonreciprocal devices in the integrated optical nanocircuits.