2006 Chevy Aveo

I have a 2006 Chevy Aveo that has the check engine light on. I was getting codes PO300,302 and 304. After having the crank sensor and ignition coil replaced and then the manifold gasket, those went away and I started getting a code PO315. I took it in for a crank sensor relearn and it would clear only to come back in as soon as the key is inserted in the ignition. Now I am being told that trigger wheel needs replacing by someone who has not even looked at the car. If that was the case wouldn’t the 315 code have been there from the beginning?