Car just threw the code P0133 which is -

rear air/fuel ratio sensor ( bank1, sensor 1 ) circuit slow response

I was reading up on some old topics and some people were saying that its the ECU and not o2 sensor? If I just replace the primary 02 sensor the light will just come back in the future and throw the same code. I also heard that honda covers a new ECU under 80k miles, which makes the sensor less sensative? What causes this code? Any help is appreciated!

oh yeah, car is a 1999 SI with bolt ons