why would check engine light come on

I was thumbing around my 08 toyota corolla's kick panel, scouting the wire colors and wire harness connectors. I unplugged several of the harness at the kick panel in curiosity, likely with the radio on, but not with the key in the ACC position. When I was all done and running to the store, my check engine light was lit. Any ideas if a short could have had caused this? Should I just pull the STOP fuse to clear the code and/or cycle my key 100 times?

i just cycled the key hundred times and cleared the code... but the question remains, will a short throw am error code?

You shouldn't unplug anything with any power on in the car. For amateurs it's a great idea to unhook the battery before unplugging anything just to reduce the chance of damaging anything. Before you "cleared" the code you should have used an OBDII code reader and read the code. Then you would know what it was and then you might have an idea of what caused it. Chances of a short causing the problem are slim to none.Kevin Pierson

The on board processors "saw" a no load or OPEN circuit not a short which would possibly had fried them. As KP says NEVER EVER disconnect ANYTHING with the ignition on.