DTC P0135: Ho2S Heater Circuit - Bank 1, Sensor 1, DTC P0141: Ho2S Heater Circuit - Bank 1, Sensor 2, DTC P0155: Ho2S Heater Circuit - Bank 2, Sensor 1 & DTC P0161: Ho2S Heater Circuit - Bank 2, Sensor 2: Description

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The Heated Oxygen Sensor (HO2S) must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the Powertrain Control Module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms, once per second. The PCM also monitors the current flow through the heater for diagnosis. This diagnostic will only run once per ignition cycle. If the PCM detects that the current is above or below a specified range, DTC P0135, P0141, P0155 or P0161 sets.