99 2.7L 4x4 SR5 Temp gauge issues

I'm no electrical expert, but I do have a little bit of experience. For the gauge to just instantly jump to that point when power is turned on, it seems like there would be a false contact somewhere in the wiring related to that temp sender unit. In the wiring harness, can you see any spots where it looks cooked from high heat or possibly cut or worn by rubbing through? Like through the firewall without the protective rubber grommet? Or excessive heat, like by the exhaust manifold or egr area?

 

It sounds like a false contact (correct word or terminology?) somewhere along the wire harness. Might be really hard to track down without being pointed in a more specific area of the harness. That's why I asked if anywhere along the harness, not just the specific wire that leads to the sensor or the sender after it leaves the harness, does the protective wrap look cooked or fried or suspect to being previously opened, etc. I don't have an fsm for my taco yet so I couldn't look at the wiring schematic to give you areas to start looking. Good luck.

 

Hey man, that's good to hear. I'm sure the nuts help ground that circuit, which sounds normal. So we did have it right in something not sending or reading the signal. Good job.