It could be many things.

You can check old posts about check engine light here on this forum. There are quite afew informative ones.
As far as I know, it could be:
1) bad o2 sensor (s)
2)exhaust pipe leaking
3) engine problem ( such as oil gel..)

The light was probably on before it was sold to you. The prevous owner might have unpluged the battery to turn the light off. It will not pass inspection if you won't get it fixed. You should go after the seller...

所有跟帖： 

• go after who? used car is sold as is. -用戶名被占用了- ♂ (0 bytes) () 04/15/2010 postreply 07:21:24

• You are right. I am not sure if he can. -iammadaboutu- ♂ (289 bytes) () 04/15/2010 postreply 07:34:05

• ok, i will do that. -majorindulgence- ♀ (0 bytes) () 04/15/2010 postreply 07:35:08

• thanks, the I saw the light on before I bought it. -majorindulgence- ♀ (24 bytes) () 04/15/2010 postreply 07:34:26

• 500 dollar, or even less? -用戶名被占用了- ♂ (0 bytes) () 04/15/2010 postreply 07:48:02