The printer MFC - 490CW says unable to init. 5A and will not print any documents

Here are the possible problems from most common to uncommon

1. you have crinked up paper inside the mechanism or some foreign object
2. pf encoder disk is in contact with the upper cover, possible encoder disk replacement
3. pf encoder board is bad, replace it.
4. replace the ink absorber box
5. replace the maintenance unit
6. replace engine unit
7. replace main board

thanks

if your not a repair person, I recommend you take for diagnostics.