They should only have the front 2, the rear ones came in as standard on the 2002/2003 modeks if im right.
Easy way to tell is whip the head unit out, if theres only 2 pairs of wires on the top iso (should be middle wires on the plug) its only wired for 2 front speakers.
If your going to add rears, your better off getting a new iso plug thats wired for 4 speakers and solder it onto the standard wires.