System Description

Primary HO2S  - For a primary HO2S, the system monitors maximum and minimum voltage, lean-to-rich and rich-to-lean response rates, and switching cycles during monitoring conditions once per driving cycle. The sensor is also monitored for activity continuously.

Secondary HO2S  - A secondary HO2S is used for catalyst monitoring and dual oxygen sensor control for fuel control system. The output voltage of the secondary HO2S is maintained to be close to target voltage by dual oxygen sensor control. With non-aged catalyst system, amplitude of the voltage changing is very narrow and slow. But along with aging of the catalyst, the amplitude is going to be wider and quicker. Then the system calculates average of the voltage during monitoring conditions once per driving cycle, and compares the average with malfunction criteria.