OBD Operation Summary for Fiesta - MotorCraftService.com

Upstream Oxygen Sensor Slow Response Monitor - Switching SensorA fuel control routine drives the air/fuel ratio around stoichiometry at a calibratable frequency and magnitude. Thisproduces a predictable oxygen sensor signal amplitude and duration used to evaluate the response time and frequencyresponse of the sensor.At each cycle, the lean and the rich duration are measured and accumulated separately. After a calibrated number ofcycles are exceeded, the accumulated lean and rich durations and periods are compared to the expected durations andperiods.Actual rich to lean switch time is compared to expected rich to lean switch time (as a function of MAF)Actual lean to rich switch time is compared to expected lean to rich switch time (as a function of MAF)Actual rich to lean switch period is compared to expected rich to lean switch period (as a function of MAF & RPM)Actual lean to rich switch period is compared to expected lean to rich switch period (as a function of MAF & RPM)CONTINENTAL REVISED: SEPTEMBER 17, 2010 PAGE 40 OF 111