DTC P0133: Ho2S Slow Response - Bank 1, Sensor 1; P0153: Ho2S Slow Response - Bank 2, Sensor 1: Description

Powertrain Control Module (PCM) continuously monitors HO2S activity for 100 seconds. During this period, PCM counts number of times HO2S responds from rich to lean and from lean to rich, and adds amount of time it took to complete transition. With this information, an average time for all transitions can be determined.

A lean to rich transition is determined when HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean transition is determined when HO2S voltage changes from more than 600 mV to less than 300 mV. A sensor that responds too slowly is most likely defective and should be replaced.