Check Engine Light

I have a 99 Malibu 2.4L edition. I installed an amp and subwoofer yesterday. I started my car this morning and drove to the store with out the check engine light on. Then started it to come home and the check engine light came on. Any ideas, the only thing I did to the engine compartment when I installed my amp is run the amps power wire to the battery. Thanks in advance

It is the Check Engine Telltale, right? The Amber/Yellow indicator with a little picture of an engine over on the right side of instrument cluster?

Maybe you have a loose battery cable now and and voltage is low. Or maybe you recently filled gas tank and didn't tighten gas cap enough - it could be lots of stuff.

This telltale often might take a couple ignition cycles for telltale to come on or go off so it might not have happened exactly when you thought.

UPDATE: I took it back to the dealer and had them check it. I turns out the ITA gasket was bad. That is just an intake gasket. So $94 later my car is running great.