03 Chevy trail blazer I need answers

You need to reset your ecm properly . When you disconnected the battery for a day the computer lost its settings if you dont teach it properly when you reconnect it it will not function . Try this disconect the battery for at least 2 hrs so the ecm dumps its settings . It actually helps drain the residual charge in the computer if you turn on the light switch while the battery is disconnected. once the car has had the the battery disconnected start it but under no circumstance touch the throttle . Let the car idle for a full 5 minutes once you hit the 5 minute mark take the car for a easy drive not running the car hard . nice and slow around the block . do not rev up the motor during this time . after a day of normal driving the ecm will have established its setting. Hope this helps