[Fireplug]

You all so called Techs had better LEARN the difference between a Steady Check engine lite and Flashing Check Engine Lite. Steady lite, the ECM,PCM,VCM, PCM2,PCM3 Has detected a sensor out of range . That could mean a sensor has failed or is telling you that something is wrong and caused the sensor it give a out of range reading.
Driving is ok but fuel milage is down and power out put is down. NO EMISSION Damage is being done.
Flashing Check engine Lite means the ECM, VCM,PCM,PCM2,PCM3 HAS dected a major emission Failer. That could be a Major misfire, fuel injector leak or what ever. But the bottom line is that the Emission system is being damaged or about to be damaged and driving it is a no-no.
Please all you so called know it alls tell me I am wrong. And when you do and some on here listens to you and melts down there truck/car or God forbid nobody get hurts.
CALL ANY GM Dealership and ask or better yet READ the most unread book in the world the OWNERS MANUAL.