Reduced power light

[opsinator]

I have 03 vue v6 awd 80 k The other day the reduced power light came on when I was just leaveing work and the enbgine would not go above an idol. When I shut it off all elctrical was dead. I check batterie and was bad put new one in it car started still the reduced power light and service engine light still on will not go above an idol.

Help please.