DTC P0151: 2/1 O2 Sensor Shorted To Ground: Description

2/1 Heated Oxygen Sensor (HO2S) voltage is monitored at a cold start, provided engine coolant temperature is less than 98°F (37°C), ambient/battery temperature is within plus or minus 27°F of engine coolant temperature and engine coolant temperature was more than 170°F (77°C) when ignition was last turned off. DTC will set in Powertrain Control Module (PCM) memory when PCM senses 2/1 HO2S voltage is less than .156 volt for 28 seconds after engine is started. Possible causes are: defective 2/1 HO2S, signal circuit shorted to ground, sensor ground or heater ground, or defective PCM.