| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology which can suppress the lowering of the measurement accuracy of an A/F sensor and a NOx sensor arranged at a downstream side of an exhaust emission control catalyst even if an unburned HC concentration of exhaust emission at the downstream side of the exhaust emission control catalyst is raised due to post-injection in an internal combustion engine and fuel addition by a fuel addition valve, and as a result, can suppress the lowering of OBD accuracy.SOLUTION: In the case that, at the execution of OBD of exhaust emission control means, unburned fuel is added by unburned fuel supply means, and an unburned fuel amount of exhaust emission at a downstream side of the exhaust emission control means is increased (S101), an amount of exhaust emission which is recirculated by EGR means is increased (S102), and after that the OBD is started (S104). |
