more than likely it is a bad o2 sensor giving you a wrong reading, or your catalytic converter is clogged up. this happened to me when i had an integra gsr and i just put a test pipe on and it went away. in your case u might wanna get it checked out by somebody cause u dont wanna spend money u dont need to. or there is this thing called an o2 simulator, basically u wire it from your o2 sensor to your ecu and it tells the ecu everything is ok, thus no check engine light...i would only recommend it if you use a test pipe or straight pipe though.