DIAGNOSTIC DEVICE AND DIAGNOSTIC METHOD OF AIR-FUEL RATIO SENSOR

摘要

PROBLEM TO BE SOLVED: To diagnose abnormality and failure of an air-fuel ratio sensor through a simple control process utilizing a suspension process for avoiding control fault of feedback. SOLUTION: Air-fuel ratio feedback control is suspended for a predetermined periodΔD1 when the control fault of feedback where a real air-fuel ratio rAFS dose not follow a target air-fuel ratio tAFS is determined during air-fuel ratio feedback control toward the target air-fuel ratio based on a sensor output of the air-fuel sensor according to the real air-fuel ratio rAFS of exhaust gas (T1). It is determined that the air-fuel sensor is abnormal when the number of suspension CLPCNT becomes beyond the predetermined reference number NGCNT while a fluctuation range (AFSMAX - AFSMIN) of the sensor output (a voltage value) of the air-fuel sensor does not exceed a reference fluctuation range. COPYRIGHT: (C)2008,JPO&INPIT