| 摘要 |
<p>PURPOSE:To improve accuracy in failure diagnosis by comparing an air-fuel ratio learning value obtained during introduction of secondary air with that obtained while the secondary air is not introduced, and thereby diagnosing failure. CONSTITUTION:A secondary air introduction device 42 introduces secondary air into an exhaust pipe on an upstream side of an O2 sensor 41 during cold time of an engine. The introduction of the secondary air is judged by a judging means 43, and based on the result, air-fuel ratio feedback controlling is carried out according to the signals from the O2 sensor 41. During introduction of the secondary air, an air-fuel ratio learning value renewal means 45 renews an air-fuel ratio learning value stored in one memory 44. While the secondary air is not introduced, an air-fuel ratio learning renewal means 47 renews an air-fuel ratio learning value stored in the other memory 46. A judging means 48 judges the secondary air introduction device 42 by comparing the memories 44 and 46 to each other.</p> |
