Company here in Ireland (Dublin) called "Lawless Automotive" they repair and sell all kinds of in-car entertainment. After my recent adventures with a set of jump leads, I finally got my stereo back today from the above mentioned . Blown microprocessor (€120+VAT), got it working and discovered faulty CD mechanism (long story).
TotaL cost for repair €533.45. Feeling a bit sore at the moment ..........
Anyway, back to the ERR 3 problem. Your stereo should be covered by the extended 5 year warranty on the stereo from Lexus. (precisely because of this problem)
Good luck,
franmac.