0155 and 0161 codes

I purchased a code scanner and these are the two errors I get every few days. How difficult (expensive) is it to change the O2 sensors and what is triggering the light?

Thanks.

I purchased a code scanner and these are the two errors I get every few days. How difficult (expensive) is it to change the O2 sensors and what is triggering the light?

Thanks.

The code is for the 02 heater circuits not a bad 02 sensor.
Check the 02 sensor heater circuit.
Check the fuse to start with and then for 12 volt power to and ground at o2 sensor plug in.
MT