When I start the engine the Idle is to lot and not stable.

So I changed my starter in my ion and it worked fine for a minute and then the battery light came on it wouldn't go off and now it's still on and I can't get it off the alternator is good the coil packs good the spark plugs are good they're all brand new and it won't it'll crank but it won't start

Yellow engine caution light will not extinguish Just had it all taken care of but. The m/x don’t have the computer for the diagnostic port.