DTC P0151: 2/1 O2 Sensor Shorted To Ground (With CALIF. Emissions): Description

2/1 Heated Oxygen Sensor (HO2S) voltage is monitored after engine coolant temperature reaches 170°F (77°C), ignition is turned off, 2/1 HO2S cools down, and after the next time ignition is turned on, engine coolant temperature is less than 98°F (37°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 2/1 HO2S voltage is less than 0.16 volt for 28 seconds after engine is started. Possible causes for DTC to set are: defective 2/1 HO2S, or defective connectors or wiring.