Isuzu Pick Up Mod 95.

How about someone who can help me to diagnose because it does not turn on my truck is an Isuzu Pickup model 95 4x4 .... What happened at the beginning was that the time band was damaged and now it changed but it turns on and almost immediately goes out it tells me the mechanic that is current but not enough and with the scanner did not come out any code
if someone could give me their opinion or guide me to the probable fault thanks ...