Check Engine Light On problems of the 2002 Chevrolet Prizm

The contact owns a 2002 Chevrolet Prizm. Two years ago, the emissions control box failed at 41,000 miles and caused the check engine light to illuminate. At 72,000 miles, the engine has a piston knock. Two different mechanics stated that the engine needed to be replaced. The engine knocking has worsened. The repair has not been made. The contact stated that he was a licensed mechanic and had regular maintenance performed on the vehicle every 3,000 miles. The purchase date and speed were unknown. The current and failure mileages were 72,000.