DTC P0137: 1/2 O2 Sensor Shorted To Ground: Description

Circuit is monitored at a cold start with engine coolant temperature less than 98°F (37°C), ambient temperature within 27°F of engine coolant temperature, and engine coolant temperature more than 170°F (77°C) on previous key off. DTC will set when 1/2 O2 sensor voltage is less than .156 volt for 28 seconds after starting engine. Possible causes are: defective HO2S, signal circuit shorted to ground or defective PCM.