Stjepan

OBD is only powertrain diagnostic,dont even see modules like airbag,media,central electronic...only engine and SOME ABS,AUTOTRANSMISION.. thats all for 20$ diag.device Airbag ecu is always in midle od the car...DONT search for it BEFORE you have diagnostic report for it...even IF its broken there will be reported as internal fault or similar description..so diagnostic first

Hmmm..batery change have nothing to do with this,you can loose some comfort setting for windov or im some car batery management need to know capacity of batery...in youre case find reverse switch (2pin) conect them and see od there reverse lights..IF yes switch od faulty,IF NO then its not problem you can solve....run some diag Tool,they are cheap now

Somewhere on gearbox under airfilter box..2 wires switch Like somekind indicator...that switch send signal that you ste im revers so engage reverse light/test park sensor at once..oil sensor is more complicated device,sends signal for level,oil temperature some od them viscosity...run some diagnostic to see what is actual fault...and YES it is bolted on oil pan,so removal means oil out..

Reverse switch die