I have a 2004 Lexus RX330 and my CD was stuck for the past month with this error Code 4 ! I tried resetting the "Ship Mode" seen on other sites by holding the "Disc" and "Seek Up" button at same time ( yeah it's a stretch for one hand ) while you turn the ignition key to ACC then press the "Load" button without any luck.
Then I saw the credit card trick and figured it's worth a shot so I stuck one in- you have to aim it down and sort of lift up on the front cover and then keep wiggling it side-to-side until you can work it almost all the way in but don't drop it inside ! Remove the card and turn off the radio and ignition key, then repeat the "Ship Mode" reset in 1st paragraph by holding the "Disc" and "Seek Up" button at same time while you turn the ignition key to ACC . My display showed "Ship Mode" and the pressed Load, then the Eject button until all my CD's were ejected. I then pressed Load button again and inserted a CD and it started playing normally again. It may not work for everyone but it saved my day. Thanks to all the contributors here.