I got P0325 and P0420 my Camry recently after replacing rear main seal.

What is your question?

I had a mechanic changed rear main seal taking out the engine. Upon done it got two codes P0325 and P0420. What could be the reason? The Autozone scan result says something wrong with knock sensor. Could it had been tempered? Where is the knock sensor located and where does the wire connected it? Any input would be greatly appreciated. No check engine light was there on the dash before the work.