s14 throwing some codes

[2slow2go]

Hi my s14 has been throwing the following codes. this is a ka24de. everything stock.

p0130- 02 circuit bank 1
freeze frame- fuel system 2 open loop-faault

and

p0325- knock sensor 2-
freeze frame- fuel system open loop-fault

Notes- i talked to the guy at schucks and he said it might be electrical circuit problem.

Before this it was throwing the o2 code and running rich. I recently had a alarm installed. And noticed that in my other thread about my heater taking really long to warm up, people said it might be the thermostat stuck open.

what maybe the problem? is it just a simple o2 sensor replacement?

thanks,
huy