can i put a used pcm in my 2002 bonneville from a 2001 lasaber, will it run

It might run, but you may lose functionality of some sub-systems like EVAP, fuel level etc. I tried to use a 96 Park Ave Ultra PCM in my 97 Bonneville. It ran, but some other things didn't work. Only way to be 100% sure is to get an Alldata subscription and compare both platforms pin for pin at the PCM.

You would be better off in the long run and find one that'* same year/same platform.

ok thanks for the response, now if i swap these out and do the security relearn and things dont work out, can i put the original pcm back in with out a hitch

Should be able to.

If the PCM is the same part number is should be fine, but I would take it to the dealer and pay the hour labor to have them reflash it with the proper VIN and software updates.

it wont run for more than a few seconds without having someone do that and some one do the security.