Swap a known good sensor from the front to the rear and scan again - this will tel you if the new sensors are bad - you'll have three bad in the rear one bad in the front....

And be thankful you have a pre-facelift (from the sounds of it) where you don't need to drop the entire front bumper to access the front sensors!!

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Wayne
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)