You need a much better mechanic
Absence of codes means NOTHING
It also sounds like the guy’s not very systematic in his approach
I’ve fixed tons of driveabity problems, no starts, stalls, etc. which never threw any any codes
I’m sure most of the professional mechanics on this website could say the same thing
Completely wrong
About 1/2 of the faulty crankshaft position sensors I’ve replaced never generated any code(s)