check engine light came on few days ago. i rent OBD2 to scan the code, and it gave out (P0150 and P0325)
i notice that p0150 is 02 sensor and P0325 is knock sensor
i clear the o2 sensor code but i can't not clear the knock sensor.
light were turn off, but do i need to replace knock sensor and o2 sensor or should i wait until light came on again?
also i notice that my fuel mileage is poor. full tanks give out only 220miles.
Does knock sensor decrease mileage? and when i push gas pedle i see fuel nidle move down but when i slow down niddle goes back up little? what cause that? is it fuel filter or pump?

help me...

 

What I would do is drive for a while and see if the o2 code comes back, if it does replace it. It's the less expensive and easier to replace than a knock sensor, and knock sensor codes have been known to go away after a 02 sensor has been replaced.

If the o2 code never comes back but you still get the knock sensor code then replace it. But I would first wait to see about the o2 code. In case you did not know, the knock sensor may trip a code without triping the CEL light. So check the codes even if the CEL goes away.

I have no idea about the gas gauge.