DTC P0133: Bank 1 Heated Oxygen Sensor 1 Circuit - Slow Response Or DTC P0153: Bank 2 Heated Oxygen Sensor 1 Circuit - Slow Response : Description

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.

The front Heated Oxygen Sensors (HO2S 1) are located in exhaust pipe, upstream of catalyst. Sensors detect amount of oxygen in exhaust gas compared to outside air. Front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. Front HO2S signal is sent to the ECM. ECM adjusts injection pulse duration to achieve ideal air/fuel ratio. Ideal air/fuel ratio occurs near radical change from one volt to zero volts.

To judge malfunction of HO2S 1, this diagnosis measures response time of HO2S 1 signal. The time is compensated by engine operating (speed and load), fuel feedback control constant, and HO2S 1 temperature index. Judgment is based on whether compensated time (HO2S 1 cycling time index) is inordinately long or not.