Circuit Description

PCM continuously monitors O2S1 activity. PCM counts number of times a lean-to-rich and rich-to-lean response is indicated, and adds amount of time all transitions took to complete. With this information, an average time for each transition can be determined.

A lean-to-rich transition is indicated when O2S1 voltage changes from less than 300 mV to greater than 600 mV. A rich-to-lean transition is indicated when O2S1 voltage changes from more than 600 mV to less than 300 mV. DTC P0133 will set when response time for O2S1 voltage to change from rich-to-lean, or lean-to-rich, is one second or more during closed loop operation.