This could be the dumbest question i've ever asked

Hi guys as some of you may know i've been trying to fix numerous problems on my sons megane II 2003 1.4 and replaced many parts including

coils

plugs

before cat lambda sensor

MAP sensor

temp sensor

also removed and cleaned TDC sensor

removed and cleaned fusebox and all wiring plug into it



the question im going to ask now is, if any of these parts were at fault they would have generated a fault code in the ECU, right?



So once i've replaced these parts, does the ECU know? as i havn't had the possible ECU codes wiped, would the ECU know the new parts are installed as they are running properly OR Do the fault codes on the ECU basically tell the replacement parts to run crap like the broken ones



I know its probably one of the dumbest questions ever but its a steep learning curve on this renault megane, and im learning new stuff about it every day.



thanks in advance (dont laugh too much please)