is there anyway this can be fixed or is the whole motor need to be replaced?

 

Depends on what is causing the knock.

 

It can be repaired just depends on what caused the knock , where it's coming from and what damage has it caused.

Dont run the engine leave it off till you find the issue and state of the engine. And if you do happen to run it don't rev the engine high. It's best if you can have a mechanic or shop look at it. Most likely they would suggest for you to replace engine.


when did you hear it knock was it on a start up or you was driving?

 

Are you basing this off of actually hearing actual knocks, or just the sensor reporting a code? If it's just the sensor it's a $20-$50 part depending if you go OEM or not. The sensor can be replaced either by removing the plenum, there's a write up here, but I've also heard of just removing the power steering pump and removing the knock sensor that way. Also, it's pretty common to have the wire for the sensor to be chewed by rodents and small animals.