CADILLAC STS WARNING LIGHT

My Car Has The Battery Light On The Dash N Says Battery Voltage High, My Question Is Whats Causing That

My Car Won't Shift After 40mph. The Service Engine Light Comes On And Gives Me The Codes S038 & S073. Car Drives Fine If I Keep It At 35mph...

What Would Be The Most Efficient And Cost Friendly Device, Availible To The Public, That Would Check Trouble Codes, And Clear The Check...