| 摘要 |
PROBLEM TO BE SOLVED: To perform abnormality diagnosing for an exhaust emission control catalyst highly accurately and by a relatively simple structure. SOLUTION: Determination is made as to whether an abnormality diagnosing condition is established or not (S1). If established, an objective air-fuel ratio is switched to another (S2). The output of a downstream side oxygen sensor is monitored (S3). Based on a degree of changing in the output of the downstream side oxygen sensor, the abnormality of an exhaust emission control catalyst is determined (S4). If normal, 'OK determined' is made (S5). If abnormal, then 'NG determined' is made (S6), and an MIL is lit (S7). Thus, the abnormality of the exhaust emission control catalyst is diagnosed highly accurately and by a relatively simple structure. |
