Catalyst Efficiency Monitor Operation
- The hybrid vehicle exhaust system uses two separate HO2S. The front HO2S is a universal HO2S and is the primary fuel control sensor. This sensor is the first HO2S in the exhaust stream and is referred to as the front or stream 1 HO2S. The last HO2S downstream in the exhaust system is used to monitor the catalyst and is referred to as the rear or stream 2 HO2S. For additional HO2S information, refer to the HEATED OXYGEN SENSOR (HO2S) MONITOR .
Typical monitor entry conditions:
- engine coolant temperature is between 71°C - 110°C (160°F - 230°F)
- intake air temperature is between -7°C - 59°C (20°F - 140°F)
- inferred rear HO2S sensor temperature, minimum of 427°C (800°F)
- inferred catalyst midbed temperature is between 482°C - 815°C (900°F - 1500°F)
- fuel level is greater than 15%
- air mass is less than 15g/sec (2.0 lb/min)
- An exponentially weighted moving average algorithm is used to determine a concern. Three DFCU events are required to illuminate the MIL during normal customer driving. If the KAM is reset, a concern illuminates the MIL in two drive cycles.