Code P0161 

Code P0161- bank two sensor two O2 heater performance.
The PCM monitors the oxygen sensors signals to adjust the air to fuel mixture. the ideal air-to-fuel ratio is 14.7:1 on a cold engine the PCM does not use the oxygen sensors signals to adjust the mixture until the sensors and the ECT or Engine Coolant Temperature reach the close-loop status that's why you smell gas when you start your car in the morning because the engine is running on an open-loop and it's running rich. the O2 sensors need to be very hot to function correctly and that's why they are equipped with heaters along with the SAI system or Secondary Air Injection system if the car is equipped with one, the temperature of the sensors and the catalytic converter rise quickly to function correctly and efficiently