DTC P0161: 2/2 O2 Sensor Heater Failure: Description

2/2 Heated Oxygen Sensor (HO2S) heater circuit is monitored with engine at idle immediately after a cold start, with engine coolant temperature less than 147°F (63.9°C) and ambient/battery temperature is within plus or minus 27°F of engine coolant temperature. DTC will set in Powertrain Control Module (PCM) memory when PCM senses 2/2 Heated Oxygen Sensor (HO2S) voltage is more than 3 volts for 30-90 seconds. Possible causes are: defective 2/2 HO2S, heater ground circuit open, ASD relay output circuit open or defective PCM.