check engine light is on .
Why does the transmissions not shift into reverse.
on 2003 Mitsubishi Diamante
Your check engine light may or may not be related tor your transmission. It is likely that there is internal failure, and in that case it is recommended that your rebuild or replace your transmission. Before guessing what could be wrong, you should take it into an all-around repair shop that also performs transmission diagnostics and repair for an expert diagnostics, since your check engine light is on and your have transmission troubles.