I had this same problem with my printer that i bought off ebay for 10 dollars. I bought the pdf service manual and it turns out that when i disassembled it i found a small connection was not plugged in all the way on the pcb that controlled the head. Here is what the manual says about the error code
5,002.42 (0x2b03): YA_POS_FAIL Y-axis position failure, the drum is not where is should be, possibly because the drum position sensor electronics have failed, or because the
motor drive or drive belts have failed, or because something is physically blocking the motion of the drum
In my case because the little plug was only half way in it could not get a correct reading on its initial position and thus came this error.
Hope this helps.
Ezra