Is it true that the temp gauge on my 2000 Z-28 is just a dummy gauge. If so WHY would GM do that. How does one tell what the engine temp is ? Doesn't seem right.

 

lol, no its not a fake gauge. test your temp sensor.

 

Testing sensor, remove terminal and measure resistance to ground/body.
Cold should read a lot of ohms, say 1 megaohms.
As sensor gets hotter, resistance goes down, say at operating temp, 200°F, resistance could read 200 ohms.
You could do the same with gauge testing, remove terminal and insert a rheostat or fixed value resistor, say 100 to 200 ohms, attach one lead to wire terminal removed and other resistor lead to ground and gauge should read closer to HOT with IGN on.

 

here is link to lt1 sensor test. I would think the ohms on yours would be close to the same. 4th Gen LT1 F-body Tech Articles

 

1998 was the last year that the dash temperature gage actually received a signal from the sending unit directly. The temp sensor had two different resistors (4 wires), one for the PCM and the other for the gage. In 1999, the sensor was changed to one resistor (only 2 wires) which sent the signal only to the PCM where the temp was calculated and then relayed to the dash gage. I read somewhere that this was done because of complaints about the temperature readings fluctuating. With this change, the gage was suppose to now show a temp range much like a light and not the actual temp, eliminating the fluctuations. A scanner will still display the actual engine operating temp. I looked in the service manual to tried to find where I read this, but haven't found it yet.