diagnostic no code??

[anthony25]

the engine management light came on on my mk3 mondeo duratec petrol last week so took the battery off replaced it after 20 mins the light hasnt come on again until today which is a week ago so removed battery again replaced it etc light stayed off had diagnostic today and read no codes also both lambda sensors working fine etc the guy said because i removed the battery it reset the ecu therefore cleared any codes that were there and told me if the light comes on again he will come out and do the check again with the light on and there will be a code there then he also said it cant be much as the cars not in limp mode or didnt go into limp mode even when the light was on the car still drives fine..the only thing he noticed was a slight tapping noise coming from the engine seems like it was coming from inside the engine near the 1st and second spark plugs etc any1 shed any light on any of this?????

[gary2411]

camsensor ok, ? could be tappet noise? plugs been checked for loseness and cleaned , here are three things
you can check