Exhaust Gas Recirculation (EGR) valves regulate recirculated exhaust volume to reduce NOx emissions. CHEPQ diagnostic tools capture position sensor feedback and actuator control signals, analyzing response time, hysteresis, and positioning accuracy under varying conditions. Deviations suggest mechanical sticking, electrical faults, or calibration drift, all of which impair emissions compliance and engine efficiency. Detailed signal analysis enables precise fault isolation and targeted repair.