L322 Really weird Parking sensor fault. No Power

I have a 2003 L322 and im having a really weird fault. I brought the car recently and had a faulty front left sensor. I replaced it and my parking sensors worked fine for a while.

I had a flat battery recently (left interior light on) since then my parking sensors do not work at all. No noise or light when put in reverse and exactly the same when the button is pressed.

I have access to autologic which allows me to recode the PDC ecu. If i recode it, it works fine until i switch the ignition off and then its exactly the same. Its as if it forgets its programmed.

I replaced the PDC ecu in the drivers side rear panel and the fault is the same still.

Has anyone come across this before?

Oh dear, front parking sensors !! what's wrong with the Mk 1 eyeball ? As for the rear, fit the towball and stop when you hear the crunch.