It's the drum thats causing the lines to happen. Youre going to have to get that replaced before you can reset the counters.
If you get light copies, then the developer should be replaced.
A line on an LCD, either horizontal or vertical usually means the video driver board is defective or the screen is defective, does it show up as black even on a dark screen? That means a line of LCD "shutter"s is not working and there is a problem that cant be fixed by a reboot or channel change. Bummer.
Here's a link to order the original the JVC upper Y-buffer board and lower Y-buffer board for this model from a major parts distributor if needed:
JVC "PD-42DX6" Replacement Part Upper Y - Buffer Board (LJ41-02760A)
JVC "PD-42DX6" Replacement Part Lower Y - Buffer Board (LJ41-02761A)
Based on the symptoms: It is possible that the Y-buffers are faulty, which may require the replacement of the Y-sus board as well. You may want to get a local technician to diagnose the unit and provide a second opinion.
try this link
see this link and try to understand the blink codes.
this will surely help you