I can't program a pk3 on my 2005 lacrosse buick

On the dash

https://www.google.com/search?q=2005+buick+lacrosse+dash+warning+lights

..

NORMANLLY AN AFTER MARKET REMOTE HAS TO BE SET TO YOUR CAR

You need a working key to start the process...start your Buick with the functional key...turn to off...wait less than 10 seconds then insert the new blank and it should program itself...a good GM parts rep can instruct you...contact them as needed...

I believe your buick has setting in the menu scroll to where it says key fob, if they took it out of your year then the dealer has to

You might try this:

http://blog.carandtruckremotes.com/2014/09/11/how-to-program-buick-lucerne-keyless-entry-remote-fob/

But if it does not work you will need to see if there is a local locksmith that can assist you.

this can be done at the dealer.

I own a 2007 Buick Lacrosse, but I imported it to Paraguay, South America. Now I bought a new Engine Start Keyless Entry Remote from Amazon, but here we do not have any GM dealer to program the unit.
I really need help to program the keyless remote control, I will appreciate very much your help.

There is no way manually program a keyless remote to this vehicle. This vehicle requires special equipment be connected to the vehicle diagnostic port to program the remote into the keyless entry module. Sorry many new cars are this way.

Both my remotes no longer work. I will be ordering new ones off Ebay and having my dealer program them. New ones from Buick are very pricey.