Check engine?

I just bought an 06 Tacoma, it has 12000 km and the check engine light just turned on the other morning, I thought I'd ask you all before I went and spent a bunch at the dealer. What are some things that might turn the light on?

 

Not tightening your gas cap will even light that up.

 

That's what the guy at the dealer said, check the gas cap, so I was just curious to know of there was any other silly little things that could cause the light

 

Go to Autozone they will read code for you. Once you have a code come back and post it. We will be able to help you better. Gas cap is first thing but honestly there are million things that can trigger light.

 

I had the CEL turn on in my wifes Subaru 200 miles after installing a K and N... Took it out and reset the light, and it has been off for 20k miles...

 

Alright I'll see If I can get my hands on one and post it. Thanks for your help