Hey guys, I've realised that when I put the car in reverse, it makes a beep but they dont really work. Sometimes they may make one set of beeps followed by a beeeeeeep. But they dont start intermittently beeping as I get close just when I get too close it suddenly goes beeep. The front ones work fine. I heard it could be one dodgy sensor causing them all to not work properly. How can I diagnose this? Does anyone know what could be wrong with them or what to check for? By the way I do not have a VAGCOM nor can I afford one atm.