Not sure what to replace, is there a sensor somewhere here. I did have a problem at same time with this. I just filled the coolant reserve and service engine light went away.

Here you go.

https://www.gmforum.com/t278915/#post1359085

Out of curiosity.. when i start my motor when warm the volt guage hangs around just above the red line (10v) and the motor runs as if 3 - 5 chambers are running, for few seconds (3-7sec) before it hits regular voltage 14v . Could it be my altenator or my coils causing that?

Your voltage is low because the idle is low. That can be upped a little with the addition of a sense wire. There'* a write up in the tech info section

Well, so far plugs, wires, and ECT sensor with no help, any suggestions?

Sorry, I can't remember what we were talking about. Could you start a new thread about your problem. It'* hard to handle two or more issues in the same thread.

try and have the ignition module tested if you haven't.