It can be many things. Can be a blown head gasket, stuck thermostat, cooling fan not working properly, water pump problem, etc.
If the check engine light is blinking that means an engine cylinder misfire has been detected
Disconnect the battery for approximately two minutes.
Have vehicle scanned to determine the problem and have codes cleared
unhook the positive on the battery for 5 min. This should reset your check engine light if it doesnt then you still have issues.
it can be of all stupid things a improperly fasstened gas tank cap
How do you reset check engine light for the 2009 Chevy trail blazer?
No, it comes on for an issue that causes an increase in emissions. See related question below.
If the check engine light is flashing off and on when the engine is running that means an engine cylinder(s) misfire has been detected . You need to have the vehicle scanned for any trouble codes to help diagnose and then repair the problem
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
disconnect the battery for 30 seconds
You can either bring it in to a Chevy dealer or use a programmer/tuner to reset the check engine light.
sounds like a possible bad idle control valve. is your check engine light on? if so get it scanned for free at autozone