front parking sensors not working

[worthy]

hi they did work now I've got message saying service required
the back ones work fine but nothing from front, ive had bumper off and checked connections they seem to be fine.
ive replace a back sensor they work as they should but no idea as to the front ones stopping working
also as not been using the vehicle when I started it up it now gives engine management warning and dtsc could this be due to battery going low charge.

[abscate]

Low battery voltage will definite light up your dash with lots of things not working. Get a good charge in it.

Hope you guys are safe

Cymru!