DTC P0141: Ho2S Heater Circuit - Bank 1, Sensor 2: Description

WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 GMC Savana Special, 2002 GMC Savana Camper Special, and 2002 GMC Savana. 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 of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM circuitry that monitors the HO2S generates a reference, or bias, voltage of 450 mV when the sensor is cold, high resistance. Once the HO2S warms up, the HO2S generates a voltage within a range of 0 mV to 1000 mV, depending on the exhaust gas oxygen content. High HO2S voltage output indicates a rich fuel mixture; low HO2S voltage output indicates a lean mixture. Once fueling goes Closed Loop, the HO2S voltage will fluctuate above and below the bias voltage. A heating element inside the HO2S reduces the time required for the sensor to reach operating temperature, and provide an accurate voltage signal.