Concerning the first two digits of the details code in xx12 to xxD0 xx=01: Y xx=02: M xx=03: C xx=04: Bk
Density value is extremely low for the ITB surface reflectivity when the new drum unit was installed. SALT sensor trouble. Dirty ITB.

Replace the SALT sensor (clean the sensor window). Replace the drum unit (check its connections). Replace the ITB (clean it).