So, short story. My water temp gauge doesn't work, brought it in to be fixed. They removed the temp sender, grounded it the gauge flew up to hot. So they replace the sender. still nothing, the scanned it, the temp is reading temps, but nothing to the gauge. My only option is bringing it to the dealer. not really looking to drop an ass load of money, anyone have any ideas of what it could be? Possible the gauges, or a bad ground in the harness?

use some gator clips to run a line from one lead to ground and another to the harness plug. If you get a signal when the harness wire is grounded then this should produce a reading. Its probably a warn ground wire. The temp wires in particular see a lot of stress. They leave the protective shell on the very front of the engine and are subject to movement any time anything on the engine is worked on.

It may have to do with the circuitry in the cluster, or possibly your coding chip as well.