Check Engine with new plugs and...

Did the search thing and nothing came up. Anyways, I swapped in some new components for the ignition system yesterday. Mopar wire, cap and rotor. The plugs are Autolite Platinum AP985. The jeep started up fine and was idling smoothly at about 600~700 RPM. Took it around the block and it drove fine. It is still running fine today but I just noticed that the Check Engine light just came on. Could someone please tell me what is going on?

BTW, the jeep runs fine before and after the swap. There is some wears on the old rotor and cap contacts. The old plug gaps are much larger than .035. The new ones are set to the correct gap before installation. Thanks!

What year XJ? Can you pull the codes using the key on, key off method? The check engine light might have tripped for something unrelated to the tune up you performed.

autozone will check your check engine light for free. It could be many things.

It's a '99 so the key on/off won't work. Maybe I should go to autozone to pull to code.