Hi Pete, it could be the amp under the front passenger seat.
They have a corrosion problem so if they are in contact with water( say from a kids drink) the corrode and can pack up all together.
Just like mine has !! however ive just lost the bass speakers in the doors.
If this is the problem a breaker will charge around £150 for a second hand unit or they are around £500 from a main dealer.
The other route is a repairer in usa $50 ish you send the old unit they send you back a refurb unit ?? seen on ebay put in saab 93 amp.
Good luck and happy new year
Mj
January 2010
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.