ic u2 functions is management the data transfer, charge, and boot ic power functions is supply power to all ic battery drain common there are have short on the machine ic or capasiotrs
Hi bro common Error 9 problem is NandFlash maybe try take off the Nandflash and than reball the Nand than put back but when you take off the Nand very carefully and whan you put back the Nand very carefully
Try others battery or try reset SMC how to : -Shut down the computer (again, full-on off here) -Disconnect the MagSafe plug from the machine -Remove the battery -Press the power button for 5 seconds and release -Put the battery back in and reconnect the MagSafe cord -Turn your machine back on with the power button hope is helpfull