My check engine light is on my car is engine speed reduced what could be the pro

When the check engine light comes on it means the computer has detected a failure and stored the information. If the engine power has been reduced it is usually the engine computer reducing power to protect the engine from the failure or the actual failed part causing the issue directly. To know for sure you would have to retrieve the fault data from the computer.

Sometimes issues with electronic throttle body assy on GM vehicles will set the Engine Power reduced light. We would need to scan the computer for trouble code and that would point us in the right direction for diagnosis.