[Mark Ruset]

Alan here is a copy of a GM Service bulletin, it sounds like your cd player will need to be sent out for repair:
CD Errors
– E20 or CHECK CD :
Cause(s): The CD player cannot focus on the disc or there is an internal focus problem.

Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If the problem is not corrected, service the unit at an ACDelco® Service Center.

– E21 or CHECK CD :
Cause(s): There is a problem with reading the disc

Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco® Service Center.

– E22 or PLAYER ERR :
Cause(s): The CD motor is not handling the compact disc properly.

Correction(s): Service or exchange the unit at an ACDelco® Service Center.

– E23 or PLAYER ERR :
Cause(s): There is a vehicle/radio communication problem or an internal radio communication problem.

Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, send the unit to an ACDelco® Service Center.

LLAI CD Changer Errors
– E30 : Focus Error
Cause(s): The CD player cannot focus on the disc or there is an internal focus problem.

Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco® Service Center.

– E31 : Tracking Error
Cause(s): There is a problem with reading the disc.

Correction(s): Try cleaning the disc or try using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco® Service Center.

– E32 : Motor Error
Cause(s): The CD motor is not handling the compact disc properly or defective magazine mounting screws are interfering with the mechanism.

Correction(s): Reload the magazine. If there is still a problem, replace the magazine. If the problem continues, back out the mounting screws. If the condition is corrected, replace the screws with shorter screws or add washers to the existing screws. If this condition still exists, service the unit at an ACDelco® Service Center.

– E33 : CD Changer Communication Error
Cause(s): There is a vehicle/radio communication problem or internal radio communication problem.

Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, determine if the problem is with the radio, the harness or the changer. Inspect for correct voltage at all connectors. If there is still an error, service the unit at an ACDelco® Service Center.

– E34 : Changer Door Open
– E35 : Changer Magazine Empty