DAB radio, no signal. Still in 5 Year Warranty, covered or not.

Hi,    

Recently purchased a 66 reg. Auris TS Excel 1.6D, all good so far but DAB radio has no signal. I have booked the car in at Toyota for a diagnostic check on Wednesday, but they say they can not tell me if the fault will be covered by the five year warranty until the checks have been completed. Sat nav and phone working fine. The car has been serviced at this Toyota garage and has the stamps in the book, I'm suprised the problem has not been highlighted before, maybe it has. Surely they would know if the radio is covered on the warranty.