Circuit Description

A Three-Way Catalytic (TWC) converter is used to maintain low emissions. PCM monitors exhaust gasses from converter using Bank 2 HO2S located in exhaust stream past TWC converter. These sensors produce an output signal which indicates oxygen capacity of catalyst. This determines catalysts ability to convert exhaust emissions effectively.

During normal operation Bank 2 HO2S signal will be far less active than that produced by Bank 2 HO2S 1. If a problem exists causing PCM to detect excessive Bank 2 HO2S activity outside of an acceptable range for an extended period of time, PCM will set a DTC. This indicates that three-way catalytic converter's oxygen storage capacity is less than acceptable range.

DTC will set when the following conditions are present:

• No AIR, CKP, CMP, ECT, engine protection, IAT, IC, injector, left bank HO2S, MAF, MAP, misfire, right bank fuel trim or transmission DTCs set.
• Engine operating.
• ECT greater than 149°F (65°C).
• IAT greater than -22°F (-30°C).
• TP sensor angle greater than 2 percent.
• Engine speed 800-3000 RPM.
• MAP 25-80 kPa.
• Engine airflow between 14-40 gm/s.
• Fuel system in closed-loop fuel control.
• PCM determines oxygen storage capability of catalytic converter has degraded to less than calibrated threshold.