You can experience HP LaserJet Printer Error Code B0605 due to booting issues. When your printer cannot boot into the ready state, you might see an error message on your screen. It can be ERROR B0601/ B0602/ B0603/ B0604/ B0605. If you are also experiencing any such error, then you need to fix it asap before it goes out of hand. The reason this error occurs is the crashed printer firmware that controls your printer tasks.
To fix this error, try the following:
1. Update the printer drivers or install the latest drivers from 123.hp.com
2. Remove and reinstall the toner and the paper tray on your printer
3. At last, if nothing works, Re-flash the printer firmware in boot mode. To perform this step, you need to have proper knowledge of your computer. If you are not sure of it, then take help from HP Printer Experts.