Thanks for the replies...

Hmm confused, so they may be after market or fitted by the manufacturer.

As it appears to be rare I guess finding someone else with front sensors on a xfire is unlikely as will getting advice on how the front ones should work / turn on.

Assuming the front ones should become live when reverse is selected, say for parking between two cars, mine either have a fault or engage a different way.

If they were in fact fitted as an option do you think there will be a wiring diagram so I could try and trace the circuit. Also does anyone know where Chysler/Karrmann would have placed the box that the sensors must plug into?