Ok let me get this straight...you bought the extended service warranty but refuse to go to the dealer for warranty service because you're afraid you might get charged for something? Have you even read through your warranty brochure to know what's covered/not covered and any deductibles (if any)?
Next time don't buy the warranty then. You're just throwing your money away if you won't go to the dealer when you have a problem - like this.
A Check engine light should never be taken lightly. Take it to dealer and get it checked by Toyota techs who can actually read the failure codes with proper Toyota equipment. Failure to do so may negate your warranty. Comprendez?