No HP documentation on your problem, no directly-HP-available service manual.
No HP Officejet Pro service manuals, period, anywhere. I did quite a long search - long enough and thorough enough that you won't need to repeat it.
No HP Officejet service manuals available on eBay.com.
This - dubious - probably irrelevant! - possible source for what you're looking for:http://www.experts-exchange.com/Hardware/Peripherals/Printers_Scanners/HP/Q_22135421.html
...this might NOT be in any way relevant to what you're seeking. I can't tell from here.
Manual called the HP Officejet Family Technical Support Solutions Guide.
Worth for your problem: unknown.
There was a service manual for an Officejet LX - a very different type of HP printer - that I found. But at present Officejet models just don't have service manuals available to the public from any source, it looks like, in general.
As for you problem: You'll have to turn it off, unplug it, take off covers, and figure out how to get at the part that is having a problem. Since this is often, too often, a pain and a waste of time (unless you've done it a lot of times before on various models of printer, even if not nec. HP), I would advise you to exhaust all possibilities of finding out what's wrong simply by opening all hatches readily openable, removing all paper trays etc. readily removable, and looking in (with a small mirror if nec., and) with a flashlight.
If there is a repetitive 'snap-snap-snap' sound when paper tries to feed from the bottom tray, also check whether the tray itself has any problem... probably not, but it's worth a try.
Usually, paper is 'plucked' off the paper stack with a roller, sometimes on a cam, sometimes not... the cam the roller is on, which has to descend enough to pick the topmost sheet off the stack, regardless of how tall the stack is to some extent, might be what is making noise and not working. If the bottom tray is removed, this may become visible enough... or perhaps not.
Good luck. If I can help you further (with some usefulness to myself and to your problem), let me know.
I hate to ask for payment for a somewhat negative result, but I did do that thorough search, and it took over half an hour.