I have a 91 Burban 350 and the engine just up and quit on me while I was driving. It gave no notice it just died. I replaced the fuel filter and fuel was delivered to the injectors, but it still won't even begin to start up. The engine rotates just doesn't fire. I checked for codes and what poped up was 4 sets of 4 flashes, so is this a code 44? Referring to the o2 mix? If so why won't it start? Any ideas to check thanks for your help