Got a pair of refurbed 4250dtn HP laserjets. One works fine, absolutely no problems. Sounds, feels and looks brand new, both of them. One of them prints fine.
The other, prints nothing, NADA, blank pages, not even any toner on the page!

Have tried all the obvious:
Existing and new toner cartridges (yes the seal strip was removed!)
Working fuser
Cold Reset on printer startup
This is all from tray 2 I might add. The rest of the printer behaviour seems fine/normal.

I am guessing its some sort of sensor or lead that is not internally plugged in...

Any ideas on what it might be before I send it back, as its going to cost us a bomb in postage!

Cheers anyone