Thank you for the reply. A mechanic has already removed the dash as he said it was faulty and needs recalibration. He now says I need them all resetting so I have asked him to return the part to me and put the car back to how it was before he started. This is where he quoted £2500 to have them all reset. He never mentioned the sensor in the back of the car nor checked it. This is why I came here to get some advice as he sees it maybe as a quick way to make money from me!