mackay

ok, so when i start up my car it runs when cold at 1100 rpm and when already warmed up at around 700 rpm (fairly normal, nothing to complain about.) however, when i have been driving it for a little while (5 minutes or so) the idle goes up to anywhere between 1800 rpm and 2500 rpm and within a few seconds my service engine light comes on, and goes off once i start driving again. i have checked my codes and i am getting a code 24, vehicle speed sensor. I have set my idle and have adjusted my tps to .54.
is there anything i am missing? what should i check next? please help! any suggestions would be great!