EOS 20D Instruction Manual
Page 153
... after you use a non-Canon lens and the camera or lens does not operate properly. 153 Error Codes If a camera error occurs, "Err xx" will be displayed on the LCD monitor. Error Code Err 01 Err 02 Err 04 Err 05 Err 99 Countermeasures Communications between the camera and lens is probably wrong with the CF card. Erase...
... after you use a non-Canon lens and the camera or lens does not operate properly. 153 Error Codes If a camera error occurs, "Err xx" will be displayed on the LCD monitor. Error Code Err 01 Err 02 Err 04 Err 05 Err 99 Countermeasures Communications between the camera and lens is probably wrong with the CF card. Erase...