DTC P0134 Or DTC P0154: Description

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

The front Heated Oxygen Sensors (HO2S1) are located in exhaust manifold. They detect the amount of oxygen in the exhaust gas compared to the outside air. The 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. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.

Under the condition in which the front HO2S signal is not input, the ECM circuits will read about .3 volt continuously. Therefore, for this diagnosis, the time that output voltage is 200-400 millivolts is monitored, and the diagnosis checks that this time is not inordinately long.