Circuit Description
WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) continuously monitors the Oxygen Sensor (O2S) 1 activity for 100 seconds. During the monitor period, the PCM counts the number of times that O2S 1 switches from rich-to-lean and from lean-to-rich. You can determine a total for all of the switches with this information. If the number of switches is too low, DTC P1133 will set.