Wait ...
"Coding all over the place."
Did your mechanic friend scan for the codes and thusly said PCM as it was coding all over the place?
But then didnt clear the codes or turn off the CEL- check engine light.
Or it was cleared and came back?

If the former, clear the codes and light.
See if they come back on after running/driving.
If so note the numbers and let members know which codes.
Cheers


Oh yeah, since cars running just go to an auto parts store to get the codes read... then codes cleared. etc.