lost keys on 2000 galant

i lost my keys on my galant and decided to fit a 2nd hand lockset trouble is how do i get the key to work with my ecu or have i gone and done the wrong thing?

I think you might have. These keys have a chip inside so you can't just replace anything yourself. UNfortunately, you have to have the dealer make you new keys, which isnt too cheap but it's the only way to go.

buy the bare key from anywhare $25 and then take it to dealer who can program it for you