I am working on a 2004 chevrolet C4500 LLY Duramax that has a transmission temp gauge off to the side but it is factory on some of these trucks so I'm told. Trans temp on the gauge buries after running for about 10 minutes. But on the scan tool the temp is reading perfect temp. already replaced the gauge and tested it with a new pcm and tcm. Cannot find a wiring diagram anywhere on this transmission gauge. Any help would be much appreciated. TIA.