I spent an hour or so programming a new master key. I had to erase all other keys, program the new master, then the valet key. Shortly after successfully doing this, the check engine light came on. Is it possible this is related and a temporary problem? I did crank the engine a bit while testing the keys.

If it doesn't go away on it's own, reset the ECU by disconnecting the battery for about 15 minutes.

Never disconnected or replaced a battery. Will it be obvious how to do that?

Figured it out. Is this just resetting the light so that if it comes on again I know it wasn't a temporary problem?

Going to take it to autozone. I just noticed there is an OBD-II code, B2795, which goes on if you insert an unregistered key. Well, I definitely did that a few times while programming. Hope that's it and I can just clear it.

OK, the OBD-II code is P1780... PNP switch malfunction. But the light is now off when I start the car once the OBD-II scanner was plugged in.

Is it possible this is a false reading due to my frequent on/offing while trying to reprogram or should I consider it to be a dying PNP switch?