I also have a sony cdx a55. I get code E-99. Let me know if anyone has can help.

My son just purchased a car with this unit fitted. Every time he goes over a small bump in the road he gets the same message. He has to stop the car, open up the back, unplug the unit, open up the cassette, then put it all back together again. This happens on every single bump. If you have received a solution to this since you posted, I would appreciate it of you could tell me what to do!