P0008 GMC -u0100

Question

Engine light on and flashing

Answer 1

P0008 Engine position system performance bank 1

U0100 Communication loss

U0100 may not need to be diagnosed farther, this can be from  a battery disconnection,and usually erase itself automatically,  As P0008 this a misalignment on one bank to the crankshaft, where a timing chain will need to be replaced.