Hi, my xj8 4.2 is having front and rear parking sensors. Since I bought the car almost 2 months ago the parking sensors did not work and I was thinking is maybe the module or a faulty sensor as whe the car is in drive or reverse the bleep in the speakers is going off,also checked all sensor9 front +back and all of them ar ticking. Suddenly one day I park at work and the front ones started to work and I was very happy, thinking the rear ones might start to work as well but they didn't. After finishing work the front ones stopped working again and did not work .Can somebody give me an idea what else I can do to fix them or an easy method to clean the contacts without to take the bumper off as I heard can be difficult. Thank you.