Toyota Repair: 96 Previa, jumper wire, diagnostic connector

Question
The check engine light has come on. I have no obvious problems with the van, idles fine, starts fine, and drives fine. How can I find out why the light is on without going to a repair shop?

I do know a bit about cars, and can usually find what I need. I would rather do it myself, so I can't be overcharged anymore. Can you give me some advice on where to start?  

Answer
Flip up the driver's seat, there is a diagnostic connector on the left side, open the cover and locate the terminals TE1/T1 and E1, place a small jumper wire between these two terminals, with the key on the check engine light will flash and reveal the trouble code, count the number of flasjes of the light, it will be a combination of two numbers, for instance a code 26 will show as two flashes followed by six then pause and either repeat 26 or show another code if there are more than one, let me know what you find and I can help decipher the code.