My stepdaughter's 2007 Mazda 5 has had a squealing noise which comes of its own accord, but when you touch the brake pedal the noise goes away. This was reported to the main dealer several times. Last week it went in for a service and they found the problem - it was the sensor on one of the front pads. The pads were only half-worn as car has only done 18,976 miles. They replaced the pads at a cost of £130, I think this was unfair and some warranty should have been given as it had been reported before.