I'm wondering if a bad ecu will not throw codes for sensors?
My old ecu thar I suspect to be bad only threw codes when my car would start misfiring, I plugged in a new ecu and after like 30 seconds got a code for my iacv.
I searched but couldn't find a answer.

 

If your "bad" ecu is throwing a miss fire code it IS "reading sensors". How else would it know there was a miss fire?

Why do you think it's "bad"?

May be the wrong ecu for the chassis engine combo but nothing of those details were mentioned.

Do the two ecu's you swapped have the same part number?

 

Yes they are both pr4-a11.
That's what I was thinking though about it reading misfires, it just didn't make sense that i never got the iacv code to pop up on the other one.

I thought its bad because I checked for codes and all I got was solid cel

 

A solid cel is code 0, bad ecu.