Parking sensors wiring

[Notebook]

My partners son has the car at present but the reversing sensors have packed in. I understand that these were not an option when the car was new. Where should I look when I get access to the car. 
looking to fit a new kit, but the existing keeps beeping in reverse so need to disable / remove it 

thanks

[FROSTYBALLS]

If they were dealer fit, there is often an on/off switch mounted in the boot lining of the car - usually near to the light cluster containing the reversing light(s). Has your son inadvertedly knocked the switch to the off position?

[flash22]

It should be in the right side rear quarter you can find the fitting instructions on toyota tech, the on/off switch was an option

https://www.toyota-tech.eu/Aim/Aim2.aspx?pubtype=AIM&menuitem=2

its listed under park assist

if it's an older car it maybe an aftermarket kit then its a case of following the wiring