APPARATUS FOR DECIDING ANOMALY IN OXYGEN CONCENTRATION SENSOR

摘要

PROBLEM TO BE SOLVED: To decide whether or not an oxygen concentration sensor is abnormal during driving by confirming that an output signal of the oxygen concentration output sensor does not show rich and lean reversals for air-fuel ratio in an air-fuel ratio feedback control drive state. SOLUTION: A CPU 6 determines a fuel injection time with the use of a drive parameter and the number of revolution of an engine. Fuel is injected into an engine 2 during only the fuel injection time. Oxygen concentration is detected by an oxygen concentration sensor 16 from a combustion exhaust gas. By repeating the process, an air-fuel ratio of a supplied mixed gas is fed back to control a theoretical air-fuel ratio. In a fail-safe process, the CPU 6 first decide whether or not a drive state of the engine 2 is in an air-fuel ratio feedback control area and then decides whether or not the drive state is in a rich drive area. When an output level of the oxygen concentration sensor 16 indicates a lean air-fuel ratio, it is decided whether or not a counted value of an anomaly decision counter is larger than a predetermined value, thereby deciding the oxygen concentration sensor 16 as abnormal.