This has to do with the paper lifter for tray three. There could be any number of problems with the lifter or tray;
1. incorrect paper size - i.e. someone loaded letter in the tray that is mannually set to legal and didn't change the manual paper slider to letter or papers stuck in the tray,
2. manual paper lifter isn't working properly, motor spring could be broken or out of place,
3. the paper tray could be broken and you will need to replace the tray.
First check that the correct size paper is loaded properly in the tray and that there is no paper detritis stuck anywhere. If the tray has the correct paper and there is not paper detritis then swap tray 2 and 3, reboot the printer and see if the problem moves with the tray - it should become a 60.02 error. If this happens then it is a tray issue. If you still get a 60.03 error then it is a tray 3 lifter motor issue, here is a link that explains what needs to be done.
A lot of the time there is a loud pronounced clicking or banging also associated with the problem. The noise happens during the paper pathway test shortly after you turn the printer on and will display the 60.xx error code instead of the ready status.