Parking sensor fault

[XR5FoMoCo]

Hi all,

2009 XR5

So I start car and all is fine, shift to reverse and get a flashing parking sensor (PS) button light & continuous high pitched fault tone whereby the PS system becomes disabled (both front and rear).

Shutting off & restarting engine often will reset PS, and fault will either return or they might work fine for a while.

When operating correctly at startup, the fronts detect as normal, but if I walk to rear of car, the rear PS cause it to fault out again.

Even when testing just a single rear sensor, say with a hand, it will usually fault the system so it’s difficult to determine if just a single sensor is faulty or if it’s deeper into the system such as the control module located behind the boot lining.

Sensors are clean and connections seem tight.

Swapping out front sensors to the rear is last resort as quite difficult to access fronts.

Have previously scanned with ELM327 Bluetooth adaptor using Forscan & Torquelite apps with no codes returned. As it's intermittent & rears only with problem I'm thinking control module or bad connection somewhere perhaps, as the speakers emit correct tone on the occasions it doesn't fault.

Am considering obtaining a single PS and substituting one rear at a time as a process of elimination?

Anyone had similar experience and/or fix?

cheers.