You need an OBD-II Code Reader/Scanner. It connects to a port on the left side of the dash, right above where your knee goes. You can get a decent one for $99.99 or less at a parts store or at Wal-Mart. Universal code listings are provided. Brand-specific codes can be found on the internet. You can also use a reader/scanner to erase a code from memory and to read the stored codes.