My check engine light came on frequently for a while with no discernable cause after a little research i found out it was the gas cap not being tightened (or not sealing well) apparently isuzu and some other foreign autos have had ongoing issues with this. so before you spend much time or money try tightning or replaceing the gas cap the reset your check engine light (although if that is the problem it should go out by itself ) i just had to make sure to give the gas cap a few extra clicks and my light hasn't come back on. I hope its the same for you. good luck!!!