Rear parktronic 2000 s class not working

[dhs9]

I have a 2000 s-class and the front parktronic works fine however the rear does not. As it says in the manual when it does not work you get the red segemnts and a tone. I found one of the rear sensors pushed in the hole and it had a large scratch across the lense. As a test I took a piece of masking tape and taped over a front sensor to see if it would give me the same red segements as the rear. When I put it in drive I did not get the malfunction indicator of the red segment and tone for hte front. Could the sensor I found pushed in and scratched cause the rear to be inop

Thanks for any help