DTC P0157: 2/2 O2 Sensor Shorted To Ground (4.0L With CALIF. Emissions): Description

2/2 Heated Oxygen Sensor (HO2S) voltage is monitored after engine coolant temperature reaches 170°F (76.7°C), ignition is turned off, 2/2 HO2S cools down, and after the next time ignition is turned on, engine coolant temperature is less than 98°F (36.6°C) and ambient/battery temperature is within 27°F (-3°C) plus or minus of engine coolant temperature. DTC will set in Powertrain Control Module (PCM) memory when PCM senses 2/2 HO2S voltage is less than .156 volt for 28 seconds after engine is started. Possible causes for DTC to set are: defective 2/2 HO2S, defective PCM, defective connectors or defective wiring.