DTC P0155: 2/1 O2 Sensor Heater Failure: Description

2/1 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 (2.8°C) of engine coolant temperature. DTC will set in Powertrain Control Module (PCM) memory when PCM senses 2/1 HO2S voltage is more than 3 volts for 30-90 seconds. Possible causes for DTC to set are: defective 2/1 HO2S, defective connectors or defective wiring.