This might sound silly but.. where are the codes located on the vehicule ? =/

 

I am pretty sure they are found in two places depending on the year. One place I know is under the lid of the center console, the other is under the lockable lid for the trunk compartment. I am sure someone knows what years/car brand you can find the exact spots.

 

Since you have a 91 it could be in either the center console or the locking compartment. It was a some time 91 year change.