Check Engine Light

The check engine light came on my '99 silverado the other day. It stays on everytime the engine is running. How do I check what code this is and where can I find a list of codes?

Thanks

Advance Auto Parts sells little handheld "code puller" computers. You might start there.

Where on the truck do I connect a code reader?

not sure

to the plug underneath the dash-to the right of the parking brake release--16 pin i beleeve

Where on the truck do I connect a code reader?

And don't disconnect battery or clear codes before you capture a freeze frame or fail history display.

Thanks