Accidently cranked the car when it was already started. I heard a loud screeching sound. Are there any negative effects from this ?

 

i think it just affects the starter.

 

just dont make a habit of it and you'll be fine. wed is right, it only affects the starter. but doing it by accident one time wont hurt anything. i think everybody's done that in a car before.

 

well my sister did that to my car but, it wasnt on and since honda keys ignitions almost turn all the way around she started the car but didnt release the key so it mad a loud anoying sounds, but yeah it should be fine as long as you dont keep doing it, well as far as my car my sister is forbidden to drive in it because shes a jynx

 

Whenever you do that you risk damaging the teeth of the starter pinion gear, and/or the gear teeth on the flywheel. It's not "okay" to do this once, it might break off a gear-tooth even the first time. Or it might not.