When i change from radio or single disc to the 6 disc changer there is an error it won't read any discs.... It wont even change discs it won't do anything really...

If your Bose 2020 radio is not connecting to your 2016 multi-CD changer and is not recognizing discs 2, 3, or 4, there are a few things you can try to troubleshoot the issue:
1. Check the connections: Make sure that the multi-CD changer is properly connected to the Bose 2020 radio. Check the connections for any loose or disconnected cables.
2. Check the disc format: Make sure that the discs you are trying to play are in a format that is compatible with the CD changer. Some CD changers may not be able to read certain formats or may have trouble reading scratched or damaged discs.
3. Clean the discs: Try cleaning the discs to remove any dust, dirt, or fingerprints. Use a soft, lint-free cloth and wipe from the center of the disc to the outer edge.
4. Clean the CD changer: Dust and debris can build up inside the CD changer, causing it to have trouble reading discs. Try using a CD cleaning disc or a can of compressed air to remove any dust or debris that may be inside the CD changer.
5. Reset the system: Try resetting the Bose 2020 radio and the CD changer. Unplug the power cords from both devices, wait a few minutes, and then plug them back in.
If none of these solutions work, there may be a problem with the CD changer or the radio. You may need to contact Bose customer support for further assistance or take the devices to a qualified technician for repair.

You have but one choice pull the unit out and send it in for repair, they do not sell parts or provide repair & troubleshooting information to the public, approved factory repair stations only.

i would try the reset button will be in the radio/cd manual for the location

have you tried factory (store bought) CD's or changed all of them out

Take it to a local car mechanic.

try disconnecting power to the radio for an hour or so. usually it is best to disconnect the battery overnight to reset the microprocessors.

disc is stuck in Delco 6 Disk Changer

you can try looking for a reset button on either or both items. the button would only be the size of a pin. you could use the tip of a pencil to reset. if you don't find this button, try disconnecting the battery for a couple of minutes to reset the system. my guess is that outside of that, you have a more serios problem. next step - unplug the changer from behind the radio and see if you still have the same problem with just the radio. and if you are behind the radio to unplug the changer, unplug the radio and plug it back in, especially if you couldn't find a reset button.

CD ERROR DISPLAYS
CD Changers
E01:
The disc magazine is not inserted in the cd changer
E02:
No disc is inserted in the disc magazine
E04:
The disc is dirty, or the disc is inserted into the disc magazine
upside down
E99 RESET PROCEDURE:
Remove CD magazine by pressing eject button on changer.
Remove all discs from magazine and re-load empty magazine into
changer. Using the Radio RESET CD system by pressing and
holding the “ON”/”POWER” button for about ten seconds, or in
earlier models the “EJECT/6” button.


FM/RF Remote Controls
E99 RESET PROCEDURE FOR REMOTES:
Remove disc magazine from changer by pressing eject button.
Remove all discs from magazine and re-load empty magazine into
changer. Press RESET button on interface unit
WAIT:
The temperature is exceeding more than 55c(130f) and the cd
changer cannot be operated. When the cd changer cools off, this
wait disappears. When the RESET button on the interface unit is
pressed, this WAIT appears for a few seconds.


IF THESE ERROR CODES STILL KEEP APPEARING
CONTACT YOUR DEALER.

I had the same problem i just decided to pull the whole thing out and get a new radio and single disc cd changer put in and so far it works fine.