* Loose or disconnected electrical connections. When you changed the starter, you may have accidentally loosened or disconnected an electrical connection. This could cause the check engine light and battery light to come on.
* Damaged wiring. The wiring to the starter or alternator may have been damaged during the starter replacement. This could also cause the check engine light and battery light to come on.
* Faulty starter or alternator. The starter or alternator itself may be faulty. This could cause the check engine light and battery light to come on.
If you're not sure what the problem is, it's best to take your car to a qualified mechanic for diagnosis and repair.