if you have a nand read already, no need to short nand pins. open jrunner,go to advanced and nand hit the nand function and erase tick em both for ur console but dont do anything else yet.plug console up to jr programmer or whatever nand reader you hav but do not plug power to console in just yet.plug power cord in so that its not all way in but you can simply snap it in rest of way with one hand while other hits go on erase at same time.if you can get it to successfully erase,u will be able to write again. may take a few times trying but wayyyyyyyy safer than trying to short nand pins.
this method has worked 100% of the time for me in the past,just a matter of timing the power plug into console and hitting erase at right time.