DTC P1133 & P1153: Ho2S Bank 1 & 2 Sensor 1 - Insufficient Switching: Description

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

The Heated Oxygen Sensor (HO2S) is a sensor used in order to detect the oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean (more oxygen), the sensor produces a low voltage signal. When the exhaust stream is rich (less oxygen), the sensor produces a high voltage signal. The PCM monitors the HO2S activity to make sure that enough lean to rich and rich to lean switches occur. A lean to rich switch occurs when the HO2S signal voltage changes from less than 300 mV to more than 600 mV. A rich to lean switch occurs when the HO2S signal voltage switches from more than 600 mV to less than 300 mV. The PCM counts the number of lean to rich and rich to lean switches for 100 seconds. This DTC indicates that the HO2S did not switch enough times.