Circuit Description

After achieving "closed loop" fuel control, a commanded air/fuel ratio of 14.7:1, RPM between 1500-3200 and airflow between 7-25 grams per second, PCM will continuously monitor the front O2S signal for 100 seconds. During this time, the PCM counts the number of rich-to-lean and lean-to-rich switches. Voltage reading should be less than 300 mV and greater than 600 mV, to be considered a switch. The number of switches along with the time to achieve these switches are used to calculate the average response time to perform each switch. This information is also used to calculate if the proper ratio of the switches is correct.