DTC P0155: 2/1 O2 Sensor Heater Failure (With CALIF. Emissions): Description

2/1 Heated Oxygen Sensor (HO2S) heater voltage is monitored with engine at idle for at least 12 seconds after a cold start, battery voltage is more than 9 volts, engine coolant temperature is less than 147°F (64°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 more than 3 volts for 30-90 seconds. Possible causes for DTC to set are: defective 2/1 HO2S, defective PCM, or defective connectors or wiring.