Why is my thermostat gauge running high?

Most likely you have air trapped in the cooling system. There's 2 bleeder screws that need to be opened while you're filling the cooling system. The 3.4L engines blow head gaskets too. So be sure to check for that too. Hope that helps! Jim

I agree with the air idea. A live data scan will bring up what the engine temperature that the computer is getting. If that reading matches what the gauge reads then all is well, but if the computer reading is lower than the gauge then you may have damaged the temperature sender for the gauge during the overheat. Once these engines have overheated strange things may start happening down the road.