Abstract
Oxygen sensor is a crucial component for closed loop engine control system. As an oxygen sensor ages or is poisoned, ECU cant control air/fuel ratio. In order to ensure proper operation, OBD-II requires diagnosing a malfunction and monitoring the sensor circuitry. In this paper, frequency domain analysis is proposed for oxygen sensor diagnosis. At frequency domain, various sensor malfunctions can be detected through frequency and amplitude of main lobe spectrum. Slow response, signal short circuit can be detected with main lobe frequency; signal deformation and smaller amplitude with main lobe amplitude. To evaluate this method, experiments are performed and the results are presented.