P0161 – HO2S Heater Performance Bank 2 Sensor 2: The Powertrain Control Module (PCM) supplies a bias voltage (approximately 450 mV) on the Heated Oxygen Sensor (HO2S) signal high and low circuits.

Based on your mechanic's diagnosis it would seem that the oxygen (02) sensor is probably faulty and needs replacing. There is no connection with the car's heater. If there is a problem with the heater ...

P0134 – O2 Sensor Circuit No Activity Detected Sensor 1 Bank 1: The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas ...