DTC P1133: Ho2S Circuit - Insufficient Switching - Bank 1, Sensor 1: Description
WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) monitors the Heated Oxygen Sensor (HO2S) activity. Within a 100 second test period, the PCM counts the number of times that the HO2S signal voltage crosses the rich-to-lean-to-rich thresholds. If the PCM determines that the HO2S did not switch enough times, DTC P1133 will be set. A lean-to-rich switch is determined when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich-to-lean switch is determined when the HO2S voltage changes from more than 600 mV to less than 300 mV.