DTC P0141 & P0161: Ho2S Heater Circuit - Bank 1 & 2, Sensors 2 (6.0L W/Isolated Ground): Description

WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, and 2002 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

This diagnostic applies only to vehicles built with isolated grounded Heated Oxygen Sensors (HO2S). The Powertrain Control Module (PCM) supplies a bias voltage of approximately 450 mV on the HO2S signal high and low circuits. When you turn the ignition to the ON position, battery voltage is supplied to the HO2S heater. As the heater reaches the operating temperature, the HO2S voltage responds by changing from a bias voltage range to the normal operation. Typically, as the HO2S reaches the operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, the HO2S voltage may possibly go above 450 mV. The PCM runs the heater test only on a cold start, depending on the cumulative air flow, and only once an ignition cycle. When you start the engine the PCM monitors the HO2S voltage. When the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time elapsed. If the PCM detects that the process took too much time for the HO2S to enter into normal operating range, a DTC sets. The time the process takes the HO2S to reach operating temperature is based on the amount of air that flows into the engine.