Can a tow bar (towing hook) or spare wheel fixed to rear door affect the operation of the rear PD1 sensor?
No because the PD1 system only detects objects that are approaching the car/antenna sensor and so it recognises that the tow bar (towing hook) or spare wheel are fixed to the vehicle and ignores these. The PD1 only starts working once the vehicle starts moving towards an object. This detection is instant and detects objects directly behind the vehicle within millimeters of your movement.