DTC P0134: Ho2S Circuit - Insufficient Activity - Bank 1, Sensor 1 & DTC P0154: Ho2S Circuit - Insufficient Activity - Bank 2, Sensor 1: Description

WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a high exhaust stream, low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the rich-to-lean and lean-to-rich transition time. A transition is defined as, the HO2S voltage changes from above 600 mV to below 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0134 & P0154 will set.